To investigate efficacy on reduction of YMDD-HBV mutation by using Chaishao Liujun Tang (Chaishao Liujun Decoction) with syndrome differentiation.Methods:360 chronic HBV patients were randomly divided into control group (60 cases),treated with lamivudine for 18 months,and treatment group (300 cases),treated with Chaishao Liujun Tang (Chaishao Liujun Decoction) together with lamivudine for 18 months.ALT recovery rate,HBeAg negative seroconversion rate,frequency of seroconversion,HBV-DNA negative seroconversion rate and YMDD mutation rates (12 months,18months) were measured before and after treatment.Results:The treatment group was significantly better in the above indices as compared with those of control group (P<0.05 or P<0.01).Conclusion:Applying Chaishao Liujun Tang (Chaishao Liujun Decoction) with syndrome differentiation can achieve good clinical efficacy in improving patients liver functions,strengthening lamivudine's inhibition for virus mutation,and reducing YMDD mutation.