The present study aimed to investigate the effect of photodynamic antimicrobial chemotherapy (PACT) mediated by hemoporphyrin monomethyl ether (HMME) on Porphyromonas gingivalis. Fluorescence spectrophotometer was used to observe the fluorescence of reactive oxygen species (ROS) produced by HMME after illumination, a colony-counting method and confocal laser scanning microscopy (CLSM) were used to observe the neutralization of P. gingivalis, HMME and P. gingivalis zeta potentials were detected by electrophoresis light scattering method. Results showed that under light, HMME mainly produced singlet oxygen (P<0.05). The survival rate of HMME-PACT group was significantly lower than the control group (P<0.05). A large amount of red fluorescence was found in PACT group observed by CLSM, indicating that HMME-PACT could effectively kill P. gingivalis. Both HMME and P. gingivalis are negative potential, which affects their combination. HMME-PACT can effectively kill P. gingivalis, which provides experimental basis for the application of PACT in clinical treatment of periodontal disease, and also indicates that it is necessary to develop new photosensitizers with positive charge in the later stage to improve the photodynamic bactericidal effect.