Squamous intraepithelial lesions generally occur in the cervix and can be classified as low-grade or high-grade, and are very closely related to cervical invasive cancer, especially high-grade squamous intraepithelial lesions, which are precancerous lesions of the cervix. Low-grade squamous intraepithelial lesions, associated with high-risk human papillomavirus (HPV) infection, can be diagnosed histologically and most of the infected individuals can regress on their own, but if symptoms are significant or persistent, appropriate treatment is also required. The intersection of cervical squamous and columnar epithelium is called the transformation zone, and this is the best site for squamous intraepithelial lesions, while the pathology of low-grade squamous intraepithelial lesions is characterized by proliferation of squamous epithelium and parabasal-like cells, with mild heterogeneity and lesions limited to the subepithelial 1/3 layer. Patients are usually asymptomatic and may occasionally present with increased vaginal drainage. Low-grade squamous intraepithelial lesions are at low risk compared to high-grade squamous intraepithelial lesions, and the diagnosis can be confirmed by cytology with periodic review and no specific treatment. If the lesions are found to be progressive or persistent for >2 years, they should be treated, either with drugs such as interferon or with ablative treatment such as freezing or laser, or cervical conization for those who meet the indications. Squamous intraepithelial lesion is an early stage in the development of cervical cancer. Screening to detect lesions and timely intervention can help prevent cervical cancer.