AIM: To develop a novel process for production of HAV in Vero cells grown on microcarriers in a bioreactor.METHODS: Vero cells infected with HAV strain W were seeded at an initial density of 1×105 cells/mL into a 7-L bioreactor containing Cytodex-I microcarriers. During the stage of cell proliferation, the following conditions were applied: pH 7.2±0.2, temperature 37±0.2 ℃, dissolved oxygen 40% of air saturation and agitation rate 40 r/min.After the stage of virus culture started, the culture conditions were altered to pH 7.2±0.2, temperature 35±0.2 ℃,dissolved oxygen 25% of air saturation, agitation rate 50 r/min and perfusion of fresh medium at a flux of 20 mL/h. During the course of fermentation, cell density, HAV antigen titre,glucose, lactate and ammonia levels were monitored. A control experiment using conventional static culture was conducted in the T150 flask.RESULTS: After a 28-d cultivation, cell density increased to 14.0×105 cells/mL in the bioreactor, 5.6×109viable cells and 4 000 mL virus suspension with a titre of 1:64 were harvested.The viral antigen output per cell unit in the bioreactor was 3-fold higher than that in the T150 flask. Meanwhile the metabolic mode of Vero cells did not change after the infection with HAV strain W.CONCLUSION: The process for production of HAV in Veto cells grown on microcarriers in a bioreactor is a novel,efficient and practical way to obtain virus antigen for vaccine purpose. This approach produces more cells and HAV antigen than the conventional static culture. With futher improvement, it is possible to be used for the production of hepatitis A vaccine.