Abstract: OBJECTIVE To observe the effect of Porphyromonas gingivalis infection on proliferation, osteogenetic differentiation and inflammation factors, such as interleukin 6 (IL-6), IL-8 and tumor necrosis factor α (TNF-α) of human periodontal ligament cells(hPDLCs). METHODS A total of 25 cases of dentes premolares were obtained from healthy volunteers who were 12-26 years old treated with orthodontic reduction treatment from Jan. 2016 to Jun. 2017 in our hospital. The hPDLCs were isolated and cultured, and the experimental group cultured with P. gingivalis for 24h, while the control group was not given any treatment. The morphological changes of the two groups were observed. The effect of P. gingivalis on the biologic structure of hPDLCs was observed by tetrazolium dye colorimetric test (MTT Test). After induced by osteogenic differentiation medium, alizarin red S staining was used for detecting the mineralization nodules deposition. The expressions of Runx2, IL-6, IL-8 and TNF-α mRNA were further measured and evaluated. RESULTS P. gingivalis survived in the hPDLCs after invading into hPDLCs, changed the cellular morphology, and had no inhibition effect on the cell proliferation. After infected of 24h with P. gingivalis and induced of 21d with osteogenic differentiation medium, the mineralization nodules deposition were successfully formed. The expression of Runx2 mRNA in P. gingivalis infected hPDLCs was inhibited detected by RT-PCR. The expressions of inflammation factors mRNA of IL-6, IL-8 and TNF-α were significantly higher than those in the control group (P<0.05). CONCLUSION P. gingivalis has no inhibitory effect on proliferation of hPDLCs, but it can affect osteogenic differentiation and expression of proinflammatory factors.