The invention relates to a recombined virus antigen of hepatitis a. The virus gene of hepatitis a is adopted by the antigen; the recombined technology of gene project is utilized to express the virus gene of hepatitis a in an escherichia coli system; the expressed protein self assembles for forming the pentamer or the empty capsid antigen of the virus of hepatitis a; the pentamer or the empty capsid antigen can be used as bacterin for the virus of hepatitis a and has the advantages of short production period, high output and low cost. The recombined virus antigen of hepatitis a of the invention can also be used for detecting the antibody for the virus of hepatitis a.