Objective To investigate the prevalence of SEN virus(SENV)infection in patients with chronic hepatitis gravis before and after plasma exchange,and its influences on liver function.Methods Two subtypes of SENV,SENV-D and SENV-H were detected in sera from 40 patients with chronic hepatitis gravis before and after plasma exchange.The changes of liver function were also tested before and after plasma exchange.Data analysis was done by t test and ehi-square test.Results Among 40 patients with chronic hepatitis gravis,SENV-D positive rates before and after plasma exchange were 27.5%(11/40)and 42.5%(17/40),respectively,and SENV-H positive rates before and after plasma exchange were 27.5%(11/40)and 50.0%(20/40),respectively,which were all significantly different(X2=4.17,X2=7.11,both P<0.05)between before plasma exchange and after plasma exchange.And after the treatment of plasma exchange,serum alanine aminotransferase(ALT)level was(164±75)U/L in SENV positive patients,which was significantly higher than that in SENV negative patients[(48±12)U/L,t=3.13,P<0.05].But there were no significant differences of other liver function indexes between SENV positive and negative groups.Condusions SENV can be transmitted via plasma exchange.SENV coinfection may influence the restoration of liver function in patients with chronic hepatitis gravia after the treatment of plasma exchange.