The five patients with subacute hepatic failure (SHF) with HBV injection, whom with severe jaundice, ascites, the serum prothrombin time activation (PTA) 25.9% - 35.2%, the serum biochemical markers: albumin (A) 22.4-34.4g/L, serum alanine transaminase (ALT) 81.8-767 u/L, aspartate transaminase (AST) 114-207u/L, bilirubin (TB) 304.6-377 umol/L, the virological markers: all cases with positive serum tests for HBsAg and HBV DNA, 3 and 1 out of 5 cases with coincidentally positive HBeAg and IgM HBcAb respectively, were all treated actively with general anti-hepatic failure therapy after admission, but they all became continuously worse and worse. After receiving Lamivudine additionally (100mg, oral, daily), out of 5 patients, three cases showed HBV DNA loss at the 20^th-62^th day, serum HBeAg and IgM HBcAb were negative in two and one at the 28^th-60^th day, respectively. The five patients had been in hospitalization for an average time of 77 days, and two and three of five cases were heal over and better at the end of hospitalization respectively. The five patients who administrated Lamivudine therapy continuously after hospital were followed up for 7.2 months (2-14 months), and were alive during the follow-up period. There were not any side effects. The study indicated that Lamivudine antiviral therapy on subacute hepatic failure caused by HBV infection might be effective and safe and with better tolerability.