The clinical manifestations of endometriosis are sometimes quite inconsistent with the degree of the lesion. Patients with very severe clinical manifestations may have mild or limited lesions, whereas patients with extensive lesions or even severe deformation of the pelvic anatomy have few clinical manifestations. According to statistics, about 70% of patients with endometriosis have typical secondary dysmenorrhea, dyspareunia or painful intercourse, infertility and menstrual changes. When endometriosis occurs in other specific sites, many other confusing clinical manifestations can occur, which seriously affect the health and quality of life of young and middle-aged women and are of increasing concern. Pain is one of the most prominent and typical symptoms of EMs patients, including dysmenorrhea, painful intercourse, acute abdominal pain, chronic pelvic pain and painful stool. 70%-80% of EMs patients have chronic pain symptoms, which not only bring mental and physical pain to patients, but also reduce their fertility and seriously affect their quality of life. The pelvic nerves include the lumbosacral and visceral nerves from the somatic nervous system. Because a large amount of pelvic pain is transmitted through visceral afferent fibers, patients are unable to accurately describe the extent, nature, intensity, and duration of pain. Pelvic endometriosis is divided into 3 main types, peritoneal, ovarian and deep nodal, and the relationship between nerve fiber distribution and pain has been reported for different types of lesions. Nerve fiber distribution was found in both peritoneal and deep infiltrative endometriosis lesions, with the deep nodular lesions having the most abundant nerve fiber distribution. The deep nodular endometriosis lesions are found in areas with rich nerve distribution, where the retrograde menstrual blood and pelvic fluid rich in various inflammatory and pain mediators are concentrated in the recto-uterine recesses and stimulate the growth of vascular nerves in the pelvic floor. Patients with ovarian endometriosis cysts show significantly less pelvic pain than patients with other types, and the nerve distribution in their lesions is not as rich as in the other two types of EMs lesions. Only in some patients with ovarian endometriosis cysts with pelvic pain, scattered nerve distribution could be detected in the cyst wall. It is suggested that the nerve distribution in the cyst wall of patients with ovarian EMs cysts can also be related to the patients’ pain symptoms.Zhang et al. examined the cyst wall of 61 patients who underwent ovarian endometriosis cystectomy and found that nerve fibers were present in the cyst wall of 31.1% of patients and the nerve density correlated with the severity of pain. The number of nerve fibers varied significantly among the different endometriosis tissues, with the number of nerve fibers in descending order: uterosacral ligament > vagorectal septum > utero-rectal fossa > peritoneum > ovary.