As a drug-mechanical combination technology, photodynamic (PDT) can achieve accurate and targeted therapy for malignant tumors and benign diseases through the production of reactive oxygen species, oxygen free radicals or singlet oxygen by photosensitizers at specific wavelengths. Compared with traditional surgery, it has the advantages of selective killing, repeatable treatment, preserving target organ function and so on. The purpose of this study was to explore the clinical value of photodynamic therapy in cervical precancerous lesions by taking the patients with low-grade cervical intraepithelial neoplasia (CIN1) with high-risk human papillomavirus (HR-HPV) persistent infection diagnosed by "three-step diagnosis and treatment procedure" as an example. Using HiPorfin as a photosensitizer, photodynamic therapy was performed 48 hours after intravenous drip. Set laser wavelength 630nm, light dose density 137.58J/cm2, transmission efficiency 1.42, output power 2w. 3cm columnar optical fiber was placed around the 2cm in the cervical canal to cover all the lesions, and the irradiation time was 900s (600s in the cervical canal and 300s outside the cervical canal). The patients were given oxygen inhalation for 6 hours after operation, and the patients were observed for itching and other discomfort, and paid attention to avoid light. Photodynamic therapy was performed again in the same way on the second day. After two months of treatment, pathological biopsy showed chronic cervicitis, indicating that the disease had been effectively controlled. Theoretically, although the patient is not the absolute indication of photodynamic therapy (that is, meeting CIN ? or CIN ?, having fertility requirements and not undergoing surgery), this therapy can remove not only the superficial lesions inside and outside the cervix, but also the potential lesions not found under colposcopy. It can also block the persistent infection of HPV by inhibiting the expression of HPV18, E6 and E7mRNA in Hela cells. In combination with Baofukang suppository, it can block HPV infection. Increase the negative conversion rate of cervical HPV and reduce the probability of recurrence after CIN1 cure. For young female patients with persistent HR-HPV infection and fertility requirements, photodynamic therapy is an effective choice for clinical treatment of CIN1.