Objective To investigate the potential of co-expression or co-delivery of HBV core gene with plasmid DNA to shift HBsAg-specific Th2 immune response induced by gene-gun to Thl type.Methods pIRES/Core, pIRES/C 149,pIRES/S,pIRES/S/Core and pIRES/S/C149 were constructed and expression of recombinant plasmids were confirmed in eukaryotic cells. BALB/c mice were immunized by gene-gun. After being boosted twice, humoral and cellular immunities in immunized mice were monitored. Results HBV core gene enhanced the HBsAg-specific Thl type immune responses in gene-gun-DNA-immunized BALB/c mice, including increasing the liter of IgG2a, ratio of IgG2a/IgG1,CTL activity as well as IFN-γsecretion. Conclusion Co-delivery or co-expression of HBV core gene with HBsAg DNA vaccine by gene gun can shift the HBsAg-specific Th2 immune response to Th1 type.