Photodynamic therapy is a type of light-excited chemotherapy. After injecting the photosensitizer into the patient’s body for a period of time, it will form a relatively high accumulation in the tumor tissue and form a concentration difference with the normal tissue. At this time, the tumor tissue is irradiated with specific wavelengths of light, and the photosensitizer absorbs the energy of photons to produce some oxidation-active molecules. The oxidation-active molecules attack the cells through oxidation, and the cells start to die for therapeutic purposes. At clinically appropriate doses, the photosensitizer itself is not toxic, and the laser light source has good controllability, and the thermal effect of the laser is weak in the treatment, and more of the photochemical effect of the laser is played. Therefore, the application of this therapy does not damage the normal tissue function of patients. Photodynamic therapy is a new type of therapy for the treatment of tumors. Since the late 1970s, photodynamic therapy has been introduced into clinical research and has made remarkable achievements in the treatment of malignant tumors for more than 20 years now. Photodynamic therapy has definite efficacy in treating malignant tumors of body surface and cavity, especially in solving obstruction caused by cancer in esophageal cancer and bronchopulmonary cancer with immediate effect. In addition, it also has good efficacy in gastric cancer, colorectal cancer, breast cancer, skin cancer, and malignant tumors. Compared with conventional treatments such as surgery, chemotherapy and radiotherapy, the advantages of photodynamic therapy are: 1. it is a minimally invasive treatment method with little trauma to the human body; 2. it has little toxic side effects, especially suitable for patients with advanced tumors and those who have poor physical constitution and can hardly tolerate surgery, chemotherapy and radiotherapy; 3. it has little damage to normal tissues; 4. it has wide indications and can be performed on all body parts that can be illuminated by laser; 5. There is no problem of drug resistance, and treatment can be repeated; 6. It can be used for palliative treatment for patients with advanced stage and improve their quality of life; 7. 10.High safety. The most likely adverse reaction is photoallergic reaction of the skin, and generally patients need to avoid light for 1-4 weeks after administration, which is not difficult for tumor patients.