Hepatitis B virus core antigen genes(HBV c) with A or T in position 3 were amplified by PCR point mutation technique and cloned into self constructed universal vector pBlueoS by blunt end ligation. HBV c gene were cleaved out through restrition sites carried by PCR primers and inserted into pSXIVVI +X3(pX3). The recombinant plasmid pX3 c1( 3 position is A) and pX3 c2( 3 position is T) were transfected into insect Sf 9 cells to transiently express c1 and c2 gene. Radio assay showed that there was no difference between these two types of genes. It is suggested that A in position 3 is important but not enough for foreign genes high expression in insect cells.