Photodynamic therapy is a new technology for the treatment of various dermatological conditions and is highly effective in the treatment of acne. 5-ALA photodynamic therapy, referred to as ALA-PDT, works on the principle that topical 5-ALA (5 amino ketovaleric acid) is preferentially absorbed by the sebaceous glands and is metabolized into a photosensitive compound, protoporphyrin IX. Protoporphyrin IX is focused on hair follicle sebaceous units and epithelial cells. Light irradiation at specific wavelengths activates protoporphyrin IX, generating singlet oxygen, superoxide anion radicals, and hydroxyl radicals. This effectively kills Propionibacterium acnes, inhibits sebum secretion, and inhibits the keratinization of epithelial cells at the mouth of the hair follicle. These three aspects of action precisely target the pathogenesis of acne. Therefore, ALA-PDT has unique efficacy in the treatment of acne. ALA-PDT is suitable for moderate to severe acne that is mainly inflammatory, and has good efficacy, few side effects and easy treatment. It can be given once every 10 days, 4 times as a course of treatment, and can be given for two consecutive courses.