It is a group of precancerous lesions closely related to cervical invasive carcinoma and reflects the continuous process of cervical carcinogenesis and development. Recent studies have found that CIN is not a unidirectional pathophysiological development process and has two different outcomes, one is that the lesions regress naturally and rarely develop into invasive cancer, and the other is that the lesions have cancerous potential and may develop into invasive cancer. Therefore, regular screening of cervical lesions is especially important. Cervical intraepithelial neoplasia (CIN) is classified into CIN I, CIN II and CIN III according to the extent to which abnormal cells occupy the entire epithelial layer of the cervix. CIN III includes cervical carcinoma in situ. It is known that cervical cancer is closely related to high-risk HPV infection, therefore, in addition to cervical cytology (TCT examination), high-risk HPV testing is also of great importance. General management principles of cervical intraepithelial neoplasia (CIN): Management of high-risk HPV infection without cervical lesions: review cytology after 6 months and review cytology and HPV after 1 year. Management of CIN-Ⅰ 1. observation: colposcopy is satisfactory; 2. treatment: physical therapy such as freezing, electrocautery and laser for lesions with erosions. Cervical canal scraping (ECC) must be done before treatment; 3. Follow-up: review cytology after 6 months, and review cytology and HPV after one year if there is no abnormality. colposcopy is needed if cytology results are >ASCUS or positive for high-risk HPV. Management of CIN II and III 1. Observation: Observation of CIN II and III is limited to the pregnancy period. Colposcopy should be performed every 2 months and again 6-8 weeks postpartum for evaluation and management; 2. Treatment: CIN II with satisfactory colposcopy can be treated with LEEP or physical therapy, but ECC must be performed before. CIN Ⅲ should be treated with cervical conization and further treatment should be chosen according to conization pathology, hysterectomy is not the preferred treatment; 3. Follow-up: cytology or cytology every 3-6 months + colposcopy, after 3 consecutive normal ones, annual cytology or cytology + colposcopy follow-up can be chosen.