Hysteroscopy is a new, minimally invasive gynecological diagnostic and therapeutic technology, because of its wide range of applications, in recent years has been rapidly known by the majority of female friends. So, what is hysteroscopy? What symptoms or diseases need to do hysteroscopy? Hysteroscopy is a kind of examination and surgery through the natural cavity (vagina – cervical canal), because of its magnifying effect on the observed area, it can directly examine the shape of the uterine cavity and intrauterine lesions and can locate the material for biopsy, so for the diagnosis and treatment of abnormal uterine bleeding is the main indications for hysteroscopy. The so-called abnormal uterine bleeding refers to bleeding originating from the uterine cavity that is inconsistent with any of the patient’s normal menstrual cycle frequency, regularity, menstrual period length, and menstrual bleeding volume. It is a very common symptom and sign in gynecology. Its causes are many, and a large proportion of patients are due to structural changes in the uterus, that is, the growth of “things” in the uterine cavity, such as endometrial polyps, fibroids, endometrial malignancy and atypical hyperplasia foci. For women of childbearing age, the structural causes of bleeding in the uterus are mainly endometrial polyps, submucosal fibroids and other benign lesions. Hysteroscopy combined with hysteroscopic resection of the lesions is the gold standard for diagnosis and treatment, and can be done at the same time under the microscope. For endometrial polyps which are invisible under the visualization of hysteroscopy, the diagnosis is clear and the resection of lesions is feasible at the same time. For perimenopausal and postmenopausal women with abnormal uterine bleeding, it is recommended to carry out hysteroscopy in order to exclude pre-cancerous or malignant endometrial lesions, as hysteroscopy has a magnifying effect, it is able to directly inspect intrauterine lesions and locate the material to be biopsied, which has greatly increased the risk of pre-cancerous or malignant tumors as compared to the traditional diagnostic curettage. Compared with traditional diagnostic curettage, it greatly improves the accuracy of diagnosis of precancerous lesions and malignant tumors, and it is also easier to find early lesions, so that the disease can be treated in time. In addition, hysteroscopy can be widely used to investigate the intrauterine factors of infertility and habitual miscarriage, to remove uterine malformations such as uterine mediastinum, to separate uterine adhesions in order to increase the fertility rate of the patients and to improve the menstrual situation; to observe the position of intrauterine device in the uterus with or without downward displacement, embeddedness, perforation, etc., and to remove it on a trial basis.