Abstract: In order to determine the effective region of large segment genome of infectious bursal disease virus for the preparation of DNA vaccine, four-recombinant DNA constructs with various combination of VP2 and VP5 fragments have been inserted into plasmid pcDNA3.1 were constructed. They were designated as VP5-5.1+VP2-3.4 (A), VP5-5.2+VP2-3.4 (B), VP2-2.5+VP2-3.4(C) and VP2-5.3+VP2-3.3 (D) respectively. Immunization assays was conducted using 1-week-old SPF chickens and DNA constructs were delivered in two ways, intramuscularly injections or via the gene gun bombardments. Chickens were primed with 100ug DNA, then boosted were given at 7days interval for two times. The chickens were finally challenged with a IBDV HK46 strain. After analyzing the neutralizing antibody and bursa-body weight ratios, the recombinant construct VP5-5.2+VP2-3.4 was found to be the most effective when given through intramuscularly injections or via the gene gun bombardments.