CIN it can be normal in appearance, but with abnormal proliferative changes in cytology or histology. It has the potential to develop in both directions. The natural course of untreated cervical precancerous lesions can show three outcomes, i.e., lesion ablation, persistent unchanged or lesion progression. Progression from CIN I and CIN II to CIN III takes about 3-8 years, and from CIN III to invasive cancer takes about 10-15 years (WHO 1985). However, recent studies have found that patients under 35 years of age have a significantly higher chance of lesion progression and a much shorter time. The risk of progression to cancer is 15%, 30% and 45% for CIN I, CIN II and CIN III, respectively. CIN has an overall 15% risk of developing into cervical cancer, which is 7 times higher than normal. CIN I or CIN II can develop directly into invasive cancer without going through CIN III. Factors affecting CIN regression: ① As CIN grade increases, its reversal rate decreases and progression rate increases. ②High-risk persistent HPV infection is an important factor in the progression of CIN. ③The reversal rate of CIN decreases with increasing age. ④The length of follow-up also affects the assessment of CIN regression, the decrease of the body’s immune function and the decrease of the ability to clear HPV infection, resulting in the persistence of HPV infection also affects the regression of CIN.