The term CIN was a widely used pathological diagnosis in the 1970s and 1980s. However, a large number of studies in the last 20 years have revealed that cervical cancer and precancerous lesions are associated with HPV infection, and further studies have revealed that CIN is not a single continuous lesion of varying degrees, but can be divided into two categories of lesions with distinctly different clinicopathological processes: low-grade and high-grade lesions. CIN still classifies cervical squamous epithelial lesions into three levels, CIN I and II corresponding to the original mild and moderate atypical hyperplasia, respectively, and CIN III including severe atypical hyperplasia and carcinoma in situ. The diagnosis of cervical carcinoma in situ has now been eliminated from the new staging of cervical intraepithelial lesions. It is now believed that cervical exfoliation cytology suggests: LSIL (low-grade cervical intraepithelial neoplasia), which includes flat and raised condyloma changes caused by multiple HPV infections, papillary immature metaplasia (PIM) at the migratory zone, and simple HPV infection; and HISL (high-grade cervical intraepithelial neoplasia) includes the original CIN II+CIN III. Low-grade lesions can be caused by more than 40 different types of HPV infection in flat warts, condyloma acuminatum is usually caused by HPV type 6 and 11 infection, and HPV viruses are in the replication stage in low-grade lesions, whereas high-grade lesions are often associated with a limited number of so-called high-risk HPV types (18, 16, 31, 45, 56). Low-grade lesions represent a variety of qualitatively different lesions with different HPV subtypes, clonality, and DNA ploidy, which mostly resolve spontaneously and rarely progress, whereas high-grade lesions represent homogeneous changes that are less likely to resolve spontaneously and more likely to develop into invasive carcinoma. The clinical treatment options for the two are significantly different. The distinction between LSIL and HSIL corresponds well with the TBS system of cervical cytology, so that cytopathologists, histopathologists and gynecologists have a common language of communication and, through cytologic screening, colposcopy and histologic diagnosis, together with HPV DNA testing, clinical physicians can decide on different treatment options depending on the nature of the lesion. In summary, as the understanding of cervical squamous epithelial lesions has increased, the diagnosis has moved from complexity to simplicity: first severe atypical hyperplasia combined with carcinoma in situ as CIN III, then CIN III combined with CIN II as HSIL. Since precancerous lesions exist for a considerable period of time before the development of cervical invasive carcinoma, performing cytologic smears to detect abnormally altered cells and treating them in a timely manner can effectively prevent the development of invasive carcinoma and greatly reduce the incidence of cervical cancer. In the United States, cervical cancer was once the number one tumor causing cancer deaths in women. Due to the widespread availability of cytology diagnostics, the incidence rate has now dropped to the eighth. In contrast, our country has done far less in this area. Principles of management of squamous epithelial lesions of the cervix Previously, the decision to perform colposcopy and biopsy, as well as HPV DNA testing, was based on the cytology of cervical exfoliated cells, and then the decision to follow up, freeze, laser resection or conical excision was based on these results. It is now recommended that patients have both cervical TCT (cervical exfoliation cytology) and HPV testing at the time of their visit, which allows for a higher detection rate and enables patients to receive timely treatment. Obstetrics and gynecology has a complex flow chart to make different management of different lesions. If physical examination and screening suggest the presence of a viable lesion, prompt medical attention is needed to further clarify or rule out possible disease, early diagnosis and early treatment.