Objective:Photodynamic therapy(PDT)has been widely concerned in the treatment of periodontal diseases and other infectious diseases because of its anti-microbial function.The main object of this present study was to evaluate the anti-bacterial efficacy of diode laser on Porphyromonas gingivalis(Pg).We also attempted to explore an optimised protocol for a safe dosage of PDT to eliminate periodontal pathogens as well as the impact on the surface of implant,so as to provide theoretical and experimental basis for PDT in peri-implantitis therapy.