Abstract: Abstract: Objective: To evaluate the antibacterial activity of ozonated oil on Porphyromonas gingivalis (P. gingivalis). Methods: Agar diffusion assay was used to investigate the sensitivity of P. gingivalis to ozonated oil. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by broth microdilution method. The effects of ozonated oil on bacterial viability, biofilm structure and cell morphology were observed by Laser confocal microscopy (CLSM) and scanning electron microscopy (SEM). Results: Ozonated oil significantly inhibited the growth of P. gingivalis with the inhibition diameter of 68.13 mm. And the MIC and MBC of ozonated oil on P. gingivalis were 0.04 mg/mL. CLSM and SEM images confirmed that after ozonated oil treatment, no dense biofilm structure was observed, the viability and density of biofilm decreased, the intact cell shape was damaged and the cells shrink and lysed. Conclusions: Ozonated oil had a strong inhibitory effect on planktonic and biofilm forms of P. gingivalis.