Chronic periodontitis (CP) is a disease caused by the chronic progressive destruction of dental support tissues mainly by dental plaque. The treatment of chronic periodontitis is limited by traditional treatments due to the small structure of oral organs, the susceptibility of bacteria to drug resistance, and the traumatic nature. Photodynamic therapy (PDT) offers advantages such as high sensitivity, minimal side effects, non-invasiveness, resistance to drug resistance, and a broad antibacterial spectrum. To overcome the limitations of traditional treatment, some scholars have combined PDT with periodontal therapy. This article reviews the principle of photodynamic therapy, the research progress of photodynamic combined therapy, and the factors affecting photodynamic treatment of periodontitis.