Endoscopic neurosurgery has now become one of the most important and active areas of minimally invasive neurosurgery. Among them, endoscopic transnasal skull base surgery using natural cavity nasal, in the case of not pulling the brain tissue, can fully expose the lesion, the maximum lesion removal, with its minimally invasive, rapid postoperative recovery and low cost advantages for the benefit of the majority of patients, and gain more and more skull base surgeons attention, will become the inevitable trend of the future development of skull base surgery. In 1981, Wigand reported the use of endoscopy for successful repair of cerebrospinal fluid nasal leakage and in 1992, Jankowski [2] reported that the endoscopic removal of pituitary adenoma became endoscopic. Jho and Carrau [3] in 1997 detailed their experience with the clinical use of the transnasal approach for the removal of pituitary adenomas. Subsequently, the techniques and indications of endoscopic transnasal approach have been developed and a series of achievements have been made through the cooperation of otolaryngologists and neurosurgeons. Although our work in this area started late, we still have achievements, and some areas have reached the international advanced level. Second, the current field of endoscopic transnasal skull base surgery endoscopic transnasal approach can be divided into standard endoscopic endonasal approach (SEEA) and expanded endoscopic endonasal approach (EEEA) [4]. SEEA is characterized by single nostril operation, extrapolation of the middle turbinate, and resection of the anterior wall of the pterygoid sinus to the saddle area, and deals with lesions such as pituitary adenoma, Rathke’s cyst, intra-saddle craniopharyngioma, and cerebrospinal fluid nasal leak. Based on this, SEEA has seen many improvements and variations depending on the location of the lesion, such as anterior pterygoid sinus hemicolectomy, posterior septal resection and double nostril operation [5]. With the further understanding of the endoscopic anatomy, the maturation of hemostatic techniques, the improvement of endoscopic instruments, and the development of skull base reconstruction materials and techniques, EEEA has emerged, and can be divided into different EEEA depending on the exposed area: 1. Transseptal approach It reveals a wide area from the coronary to the optic cross sulcus, which has fewer important anatomical structures and is easily and safely exposed. The advantages of this approach are that it does not affect the neural tissues, prioritizes the blood supplying arteries, and allows for complete excision of the tumor and its invading bones and dura mater. 2. Transsphenoidal platform saddle node approach By removing the bones of the pterygoid platform and saddle node, the suprasellar pool and the anterior pool of the optic cross can be exposed. Thus, it is possible to remove meningioma of the saddle node, pituitary adenoma and craniopharyngioma in the supra-saddle area and three ventricles, and perform decompression of the optic canal. The advantage of this procedure is that it is performed in the direction of the tumor growth axis without pulling the brain tissue, and can clearly expose and protect important structures such as the optic chiasm, pituitary stalk, hypothalamus and superior pituitary artery, and separate the adhesions between the tumor and the surrounding blood vessels and nerve structures under direct vision. Our department was the first in China to use the enlarged approach to deal with the suprasellar region of the three ventricles of the craniopharyngioma, and the patient had less postoperative endocrine disturbance and satisfactory results [6]. 3. Transsphenoidal cavernous sinus approach In 2004, Jho et al [7] conducted an anatomical study and clinical application of endoscopic transnasal approach to the cavernous sinus region, which confirmed the feasibility of this approach. Since the arteriovenous nerve, trigeminal nerve, and talocrural nerve are located on the lateral wall of the cavernous sinus, EEEA can avoid pulling the brain tissue and the above mentioned cranial nerves, and facilitate the management of pituitary adenomas and chordomas that invade the cavernous sinus from the medial side. 4. Trans-posterior bed protrusion approach Exposure of the interpeduncular pool is achieved through the removal of the superior slope, posterior bed protrusion, and dorsal saddle bone. For posterior saddle type of craniopharyngioma, pituitary adenoma and meningioma and chordoma in the upper slope region can be handled. This region is difficult and traumatic for transcranial surgery regardless of the approach, and the advantage of EEEA for this region is the exposure of the posterior pituitary region by moving the pituitary gland upward, which plays a very important role in the protection of pituitary function. kassam et al [8] reported 10 cases in which exposure of the interpeduncular pool was achieved by moving the pituitary gland and pituitary stalk, and the postoperative pituitary function was less affected. 5. Transslope and rock-slope approaches The advantages of endoscopy for this region are clear exposure, identification of anatomical structures and simultaneous management of bilateral lesions to increase the rate of total dissection. This approach involves the bones of the middle and lower slope and the apical part of the rock, and allows exposure of the anterior and extended pontine pools. The lesions in the rock-slope region mainly involve chordoma, chordosarcoma, meningioma and cholesteatoma and metastases. The lesions in this region were reported to be treated with EEEA with good results [9]. 6. Craniocervical junction region This region involves the greater occipital foramen, occipital condyles, jugular foramen, dentate and C1 and C2 bones, and lesions in these areas mainly include meningioma in the greater occipital foramen, paraganglioma in the jugular foramen, chordoma and dentate malformation. The transnasal approach can expose the inferior slope to the superior margin of C3, better reveal the dead space under the microscope, first reveal the tip of the dentate process, its operation along the midline has less interference with the vascular nerve, and can be nourished through the mouth as soon as possible after surgery, and other advantages. The surgical approaches to this region mainly include the maxillary sinus approach and the enlarged pterygopalatine foramen approach, the scope of which is different. The lesions in this region mainly involve nerve sheath tumors, angiofibromas, chordomas, etc. Endoscopic transnasal skull base surgery related equipment and techniques 1, endoscopic transnasal access surgery has the incomparable advantages of microsurgery has been reported in many, and gradually become consensus. But there are some related equipment and technical requirements. The choice of endoscope, for transnasal approach endoscope is commonly used 0 degree and 30 degree, diameter 4mm, length 18-30cm rigid endoscope without working channel, sometimes need 2.7mm diameter endoscope, 45 degree and 70 degree endoscope can observe some dead angle in carrying out complex surgery. The brightness of the light source of the endoscope is very important, 300 degree xenon lamp to meet the needs of skull base surgery, even if the same endoscopic light source, endoscopic lens different, the brightness of light will be different. In addition to common endoscopic instruments high-speed grinding drills and neuronavigation systems are essential equipment for endoscopic transnasal access skull base surgery. Ultrasonic knife is useful for solid tumors such as meningioma. In terms of endoscopic transnasal approach operation technology, most of them advocate the cooperation mode of “two people and four hands”, on this basis, they still emphasize the use of microscopic separation technology for tumor resection. 2. Endoscopic hemostasis and skull base reconstruction Kassam [10] summarized the experience of 400 surgical cases, and proposed the use of gun-type bipolar in endoscopic surgery in terms of hemostatic instruments. In addition specially designed hemostatic clips can be used. Many materials for compression hemostasis are also essential, such as Avitene,Floseal, Syvek, etc. For venous bleeding, warm saline flushing is used for mucosal bleeding, bone wax or high-speed abrasive drilling is used for bony bleeding, and “sandwich” compression is used for venous sinus bleeding. For arterial hemorrhage, two physicians are required to work together to aspirate the bleeding from the operative field while flushing with warm saline, and to stop the bleeding with bipolar electrocoagulation or hemostatic clips after identifying the bleeding site. Standard endoscopic transnasal approach to saddle base reconstruction is relatively simple; the huge skull base defect caused by enlarged transnasal approach will definitely lead to a series of serious complications such as cerebrospinal fluid leakage, intracranial infection and meningeal bulge, and skull base reconstruction is a problem that must be solved. The key of reconstruction technology is the material and method of reconstruction. The ideal reconstruction material should have good plasticity and be strong and flexible, tissue stable, and not affect MRI or CT examination results. For example, LactoSorb (a synthetic material of 82% polylactic acid and 18% polyglycolic acid) is easily plasticized at 70°C, becomes firm when restored to room temperature, and can be self-absorbed within 1 year [11]. Alternatives to dura mater such as the treated human heart envelope Tutoplast and the collagen matrix Duragen also have the advantage of being flexible and easily trimmed. Autologous mucosal flaps with a vascular tip are also an important recent emerging repair, the most used being the Hadad-Bassagasteguy Flap (HBF) with a tipped nasal septum, which meets the majority of reconstruction needs for skull base defects [12]. The main reconstruction method currently used is the multilayer repair method. Multiple layers are filled between the arachnoid and the dura, between the dura and the skull base, and between the skull base and the nasal passages to form a firm reconstructive layer. It has been reported that multilayer reconstruction combined with tipped nasal septal mucosal flap and balloon support technique can reduce the incidence of cerebrospinal fluid leakage from 50% to less than 5%. 3. Preoperative perfect imaging assessment Preoperative imaging examination to understand exactly the size, lateral extension, blood supply, texture, adhesions and important nerve, vascular, dural and other structures adjacent to the lesion is beneficial to the safety of endoscopic transnasal cranial base surgery implementation. Careful preoperative imaging of nasal structures is necessary and essential, not only to prevent complications, but also to help in the selection of the surgical approach and the determination of the surgical plan. The development of new imaging techniques to improve the assessment of the surgical approach and the lesion itself will enable the operator to simulate the surgical procedure and develop a realistic surgical plan, as well as to assess the surgical risks and try to avoid them before surgery. Fourth, China’s endoscopic transnasal skull base surgery still needs to focus on solving the problem of China’s endoscopic transnasal approach to the skull base surgery, although a late start, in recent years has made great progress, but not yet popular. The reasons for this status quo are many. However, the following reasons are the main ones: 1) lack of cooperation between neurosurgeons and otolaryngologists, most of them are in a solitary state, and it is difficult to complement each other’s strengths. 2) conservative concept that microsurgery is fully competent for skull base surgery. 3) lack of limitation of endoscope and related instruments in early stage, which makes neurosurgeons lose confidence in endoscopic surgery. 4) insufficient training and communication. 5) lack of endoscopic endoscopic surgery. ) Difficulties in hemostasis and skull base reconstruction in endoscopic transnasal approach surgery. Endoscopic transnasal approach to skull base surgery has advantages over traditional microsurgery, which can be called “small hole, but the sky is big”. However, in addition to fully understanding and recognizing the advantages it has, we must also be aware of its shortcomings, avoiding the shortcomings, combining hospital equipment and doctors’ experience, and carrying out this technology step by step. It is believed that with the progress of concept, improvement of equipment, increase of domestic and international exchange, accumulation of experience and progress of technology, through close communication and cooperation between neurosurgery and otorhinolaryngology, the indications of endoscopic transnasal skull base surgery in China will be further expanded and the technology will be further improved, and more and more neurosurgeons will devote themselves to the cause of endoscopic skull base surgery, so that China’s The level of endoscopic skull base surgery in China will catch up with the international advanced level.