The formal treatment of acne (commonly known as pimples) begins with grading and grading. For moderate to severe acne, the most advanced, safe and efficient treatment is photodynamic therapy. Photodynamic therapy is an advanced technology that uses “photodynamic damage” to treat the disease. In other words, under the action of oxygen, photosensitizers, and specific wavelengths of light, cytotoxic substances are produced that only kill abnormal cells and tissues, while having almost no effect on normal tissues. The principle of action is that the topical photosensitizer 5 amino ketovaleric acid can be preferentially absorbed by the sebaceous glands and metabolized into a photosensitive compound, protoporphyrin IX. Protoporphyrin IX is focused on hair follicle sebaceous units and epithelial cells. Protoporphyrin IX is activated by light irradiation at specific wavelengths, generating singlet oxygen, superoxide anion radicals, and hydroxyl radicals. This effectively kills Propionibacterium acnes, inhibits sebum secretion, and inhibits keratinization of epithelial cells at the mouth of the hair follicle. These three aspects of action precisely target all the pathogenic aspects of acne. Therefore, photodynamic therapy for acne has unique efficacy. It is also effective, has few side effects, and is easy to treat. One treatment every 7-10 days, 4 times is a course of treatment, usually only 1-2 courses of treatment are needed.