Abstract: Objective To explore the role of interleukin-17(IL-17) in the pathogenesis and progress of chronic hepatitis B virus(HBV) infectious diseases, especially in liver fibrosis. Method Serum IL-17 level and liver fibrosis index type IVcollagen, LN，HA，type IIIcollagen was determined by enzyme linked immunosorbent assay(ELISA). IL-17 mRNA expression in peripheral blood mononuclear cell(PBMC) was analysed by reverse transcriptase-polymerase chain reaction(RT-PCR).IL-17 expression in liver was measured by immunohistochemistry. Result Serum IL-17 protein levels and IL-17 mRNA expression of PBMC in four HBV infectious groups (P<0.01each) were higher than in normal control. IL-17 and IL-17 mRNA in LC was higher compared with other groups(p<0.001 each). Liver IL-17 expression and serum fibrosis index raised as severity of disease with LC higher than CHB,CHB higher than ASC(Liver IL-17 expression p<0. 01 each, serum fibrosis index p<0. 001 each). IL-17 mainly located in portal area and was associated with fibrosis extent closely. Lymphocyte, fibroblast and sinusoid endotheliocyte were stained positively. Liver IL-17 expression was correlated with serum fibrosis index type IVcollagen, LN，HA，type IIIcollagen positively(r=0.883，0.834，0.793，0.722，P <0.01each) Conclusion IL-17 may contribute to the development of HBV infectious disease especially to the pathophysiology of LC.