Abstract: Four-week old SPF chickens were inoculated with fowlpox virus vaccine coexpressing gene S1 of infectious bronchitis virus (IBV) and the chicken interferon-γ gene(rFPV-IFNγS1). SPF chickens were challenged with a heterologous IBV strain LSC99I to investigate protective efficacy of the recombinant virus to heterologous virus after three weeks postinoculation The results showed that chickens immunized with rFPV-IFNγS1 developed IBV specific antibodies in serum one week after immunization, the ratio of CD4⁺ and CD8⁺ T lymphocyte in chicken’s peripheral blood of immunized group was a little higher than that of the nonvaccinated group, but the difference was inapparent.Morbidity and mortality of immunized group were 50% (5/10) and 20% respectively after challenge with LSC99I compared with 100% (10/10) and 50% (5/10) of non-vaccinated group,chickens in immunized group had slighter pathological changes when compared to that of non-vaccinated group, but the difference was indistinctive. The length and titer of virus shedding for two groups showed no significant difference. Bodyweight analysis indicated that chickens in both groups showed inapparent weight change before challenge; after challenge, chickens in immunized group had a higher weight gain than chickens in non-vaccinated group. In conclusion, rFPV-IFNγS1 cannot protect chickens against the challenge of heterologous IBV strain LSC99I although it can produce IBV-specific antibodies in chickens, chicken IFN-γ is well expressed in vivo and play a role in immunomodulatory which can alleviate the effect of recombinant virus immunization on chicken bodyweight gain.