Abstract: To evaluate the clinical efficacy and study the mechanism of combining plasma exchange (PE) and on-line continuous veno-venous hemofiltration (CVVHF) in treating patients with chronic severe viral hepatitis B.64 patients suffering from chronic severe viral hepatitis B were divided into 3 groups randomly.23 patients were treated with plasma exchange plus continuous veno-venous hemofiltration (group A) .21 patients were treated with plasma exchange alone (goup B) .20 patients received routine treatment (group C) .The efficacy of treatment and survival rates of the three groups were analyzed after artificial liver support system treatment.And the laboratory examination and the degree of hepatic encephalopathy were investigated.In group A, 6 of the 10 patients in coma regained normal consciousness (60.0%) and their survival rate was 45.5%.There was statistically significant difference between group A and B.Routine treatment uniting PE and online CVVHF on treating patients with chronic severe viral hepatitis B could increase survival rate.This therapy was a safe and promising technology and should be used as chief method of artificial liver support system.