Abstract: OBJECTIVE To explore the relationship between Pseudomonas aeruginosa virulence factors and expression levels of Toll-like receptor 9（TLR9） and programmed death ligand 1（PD-L1） in patients with chronic periodontitis. METHODS A total of 128 patients with chronic periodontitis who were treated in Yichun People's Hospital from Feb 2018 to Feb 2021 were recruited as the study subjects, the prevalence of P. gingivalis infection was determined, the P. gingivalis virulence factor gingival proteinase K（Kgp）, peripheral blood TLR9, PD-L1 and periodontal heath indexes were detected. RESULTS Among the 128 patients, 114 were tested positive for P. gingivalis, with the positive rate 89.06%. The percentage of the Kpg-positive patients, expression levels of peripheral blood TLR9 and PD-L1 and the periodontal health indexes attachment loss（AL）, probing depth（PD） and sulcus bleeding index（SBI） of the P. gingivalis-positive patients were higher than those of the P. gingivalis-negative patients（P＜0.05）. The PD-LI and AL were positively correlated with the P. gingivalis infection（P＜0.05）. The TLR-9, PD-L1, AL, PD and SBI of the Kpg-positive patients were higher than those of the Kpg-negative patients（P＜0.05）; the TLR9, PD and SBI were positively correlated with the Kpg（P＜0.05）. Among the patients with P. gingivalis infection, the percentage of Kpg-positive patients, TLR9, PD-L1, AL, PD and SBI of the patients who were effective for treatment were lower than those of the patients who were not effective for treatment（P＜0.05）. Receiver operating characteristic（ROC） curve analysis showed that the areas under curves（AUCs） of Kpg, TLR9, PD-L1, AL, PD and SBI were respectively 0.576, 0.887, 0.894, 0.858, 0.757 and 0.896 in prediction of curative effect on the chronic periodontitis with P. gingivalis infection. CONCLUSION The P. gingivalis surface virulence factor Kpg of the patients with chronic periodontitis is closely associated with the expressions of peripheral blood TLR9 and PD-L1 as well as the periodontal health. The virulence factor Kpg, peripheral blood TLR9 and PD-L1 and periodontal health indexes can be used for prediction of curative effect on the patients with P. gingivalis infection.