Endometrial hyperplasia occurs mainly in women of childbearing age. Abnormal menstruation is the prominent symptom of this disease, often manifested as irregular vaginal bleeding, scanty menstruation or heavy vaginal bleeding after a period of amenorrhea; young women may experience post-marital infertility. Endometrial hyperplasia is a group of proliferative lesions that occur in the endometrium and only a few can slowly develop into cancer. The causes of endometrial hyperplasia are mainly related to long-term estrogen stimulation, for example: the endometrium is in a proliferative state for a long time due to non-ovulation and lack of cyclic secretion phase transformation; the organism is stimulated by high levels of estrogen from endogenous (such as endocrine functional tumors in the ovaries or pituitary gland) or exogenous (such as estrogen supplementation therapy, etc.). In clinically suspicious cases, endometrial scraping should be performed for histologic diagnosis. Histologically, endometrial hyperplasia is classified as simple hyperplasia, compound hyperplasia and atypical hyperplasia. Proliferative lesions characterized by heterogeneous changes in cell morphology are called endometrial atypical hyperplasia and are classified as mild, moderate or severe according to their degree of lesion. Simple hyperplasia and compound hyperplasia have no cellular heterogeneity, but the degree of glandular structural changes varies. Simple hyperplasia is thought to be a physiological response of the endometrium to the high estrogenic state of the body and is most commonly caused by anovulatory menstruation, which often occurs in women at the beginning of menstruation or before menopause. If ovulation occurs or progesterone treatment is used, the lesion can regress and return to normal and generally does not develop into cancer. A few of the compound hyperplasia may develop into atypical hyperplasia, which may affect the prognosis. The cancer rate of atypical hyperplasia is 23%, and the cancer rate of severe atypical hyperplasia can reach 30%~50%, so it is classified as precancerous lesion. Among the 17 cases of atypical hyperplasia under 40 years old observed in Peking Union Medical College Hospital, 3 cases were severe, among which 2 cases had interrupted treatment several times after diagnosis and were confirmed to have developed into endometrial cancer when the uterus was removed in the 6th and 8th years; while among the cases of mild or moderate atypical hyperplasia, the response to drug treatment was good and fast, and after adhering to treatment, some cases could still conceive and complete childbirth, and none of them developed into cancer. None of the cases developed into cancer. After drug treatment, the endometrial lesions become mild or return to normal, and even pregnancy is possible, but there is still a possibility of recurrence after stopping the drug or after delivery. Among the 80 cases of pregnancy after treatment at Peking Union Medical College Hospital, 6 cases recurred two years after delivery, and the hysterectomy confirmed that they were still endometrial hyperplasia. This tendency of recurrence may be related to the failure to fundamentally correct the factors that cause high estrogen levels in the body. In conclusion, the majority of patients with endometrial hyperplasia have a good prognosis after aggressive pharmacological treatment. For patients with moderate-to-severe atypical hyperplasia, they should be closely followed up during treatment, and if a few cases with poor outcome are found, hysterectomy can be performed in time to avoid the development of cancer.