LEEP knife, or cervical loop electrosurgery, was pioneered by French scholars. LEEP knife has the advantages of being quick, easy, inexpensive, with few complications, and easy for outpatient consultation. LEEP knife as a diagnostic method can be applied to the following indications: 1. those with ASCUS cytology and no obvious abnormalities on colposcopy. 2. those with high degree of squamous intraepithelial neoplasia suspected on cytology or colposcopy. 3. those with unsatisfactory colposcopy and abnormal cytology. The indications for LEEP knife treatment are mainly as follows: 1. persistent CIN grade I without follow-up conditions or CIN I with high-risk HPV infection. 2. CIN grade II. 3. moderate to severe atypical hyperplasia of CIN III. LEEP knife is not applicable to carcinoma in situ, especially adenocarcinoma in situ.