Objective: To investigate the changes of peripheral Th17 and Treg and Th17/Treg balance in patients with chronic hepatitis B virus(HBV)infection, and to explore the possible role in the development of chronic HBV infection.Methods: From November 2013 to December 2015, we enrolled 142 patients with chronic hepatitis B virus infection who received treatment in the First Affiliated Hospital of Kunming Medical University.Among them, there were 23 patients with chronic asymptomatic HBV carrier(ASC group), 51 patients with chronic hepatitis B(CHB group), 37 patients with HBV-related liver cirrhosis(LC group), and 31 patients with HBV-related hepatocellular carcinoma(HCC group).In the same period, 26 healthy people were enrolled in the hospital as normal control group.Flow cytometry was used to determine the expression rates of peripheral Th17 and Treg and Th17/Treg.RT-PCR was employed to determine HBV-DNA load, and fully automatic biochemical analyser was employed to detect ALT, AST and TBIL.Results: CHB group, LC group and HCC group were higher than normal control group and ASC group in the expression rates of peripheral Th17 and Treg(P<0.05); LC group was higher than CHB group in the expression rate of peripheral Th17, and HCC group was lower than CHB group and LC group in the expression rate of peripheral Th17(P<0.05); HCC group was higher than CHB group and LC group in the expression rate of Treg(P<0.05); HCC group was lower than normal control group, CHB group and LC group in peripheral Th17/Treg(P<0.05).CHB group, LC group and HCC group were lower than ASC group in serum HBV-DNA load(P<0.05).CHB group, LC group and HCC group were higher than normal control group and ASC group in the levels of ALT, AST and TBIL(P<0.05); LC group was higher than CHB group in the levels of ALT and TBIL(P<0.05); HCC group was lower in ALT level and higher in AST level than CHB group and LC group, and HCC group was lower than LC group in TBIL level(P<0.05).In CHB group, the expression rate of Th17 was positively correlated with the levels ALT, AST and TBIL, and Th17/Treg was positively correlated with the levels of ALT and AST(P<0.05); in LC group, the expression rate of Th17 was positively correlated with ALT level, and the expression rate of Treg was positively correlated with the levels of ALT and AST(P<0.05); there was no other linear correlation(P>0.05).Conclusion: Th17 and Treg play an important role in the occurrence and development of chronic HBV infection related liver disease, and the imbalance of Th17/Treg may be closely correlated with the progress of chronic hepatitis B, which providesa basis for further clinical research. Copyright © 2016 by the Chinese General Practice.