Abstract: Objective To study the antiviral effect of entecavir in patients with severe chronic hepatitis B.Methods Eighty patients with no prior history of antiviral therapy were divided randomly into two groups: entecavir group (40 cases), and control group (40 cases).The dosage in the entecavir group was 0.5 mg/d,and the treament duration was 48 weeks The effects of entecavir group and control group on ALT,AST,TBiL,ALB,PTA,e antigen seroconversion rates,HBV DNA were observed during the treahnent.Results Afterl-weeks treahnen the levels of ALT,AST,TB iL,ALB,PTA,e antigen seroconversion rate and HBV DNA for subjects in entecavir group were 54.06,6Z 52,39 63,35.45,62.08,24.34 and 6.43,while those for subjects in control group were 76.86,95.67,89.02,31.56,42 89,32 24 and 21.12,resprctively,with significant differences between the two groups.After 24 weeks treahn ent,the levels of ALT,AST,TBiL,ALB, PTA,e antigen seroconversion rate and HBV DNA for subjects in entecavir group were 50.06,65.02,38.97,36.45,65.08,4.67 and 2.40,while those for subjects in control group were 70.86,80 52,67.02,33.06,45.76,30.78 and 10.12,resprctively,with significant differences betty een the two groups The mortality rate in entecavir group and control group were 2.5% and 22.5%.After 48 weeks treament,the levels of ALT,AST,TBiL,ALB,PTA,e antigen seroconversion rates and HBV DNA for subjects in entecavir group were 40 58,54.23,38.07,38.43,70.18,3.57 and 0,while those for subjects in control group were 56.67,75.52,69.09,33.98,59.86,24.86 and 14.12,resprctively,with significant differences between the two groups Them ortality rate in entecavir group and control group were 5% and 32 5%.Conclusion Entecavit is safe and effective in the treahn ent of severe chronic hepatitis B.