Abstract: Objective To discuss porphyromonas gingivalis (Pg) infection and expression of NLRP3, IL-1β, IL-18 in human periodontal ligament cells with chronic periodontitis. Methods Fifty cases of patients with chronic periodontitis and50 cases of periodontal healthy people were selected.Real-time fluorescence PCR technique was used to detect gingival plaque Pg, Chronic periodontitis patients after tooth extraction in periodontal membrane of the periodontal ligament cell culture, Some cells were used for Pg standard strains infection, some don't do processing of infection.The protein level of NLRP3 was determined by Western blot, the protein levels of IL-1β and IL-18 were measured by ELISA. Results Positive rate were 84.00% of pg in chronic periodontitis, positive rate were 22.00% of pg in periodontal healthy people.Probing depth of 5, 6, 7 mm, Pg concentration were 4.38 ±0.81, 4.79 ±0.76, 5.47 ±0.63 in chronic periodontitis, Pg concentration were 0.38 ±0.12, 0.46 ±0.15, 0.72 ±0.20 in periodontal healthy people.The difference was statistically significant (P < 0.05).NLRP3, IL-1β and IL-18 concentration were 1.25 ±0.12, (1 820.42 ±425.57) pg/ml and (311.55 ±45.70) pg/ml in human periodontal ligament cells with Pg infection, 0.74 ±0.08, (1 138.65 ±350.76) pg/ml and (124.70 ±42.54) pg/ml in human periodontal ligament cells with Pg non-infection, The difference was statistically significant (P < 0.05). Conclusion Pg microbial infection rate and infection were higher in chronic periodontitis, Pg infection can cause NLRP3, IL-1 beta, IL-18 expression increases in human periodontal ligament cells.This may be one of the reasons for Pg cause chronic periodontitis.