NP gene of AIV was amplified by PCR and cloned into the expressing plasmid pSOC, where NP gene was fused to 3′end of T4 phage small outer capsid gene encoding SOC protein. T4 phage expression vector named pSOC-NP was constructed and used to transform E.coli BL21(DE3). The recombinant E.coli BL21(DE3) was induced by IPTG. The expressed fusion protein SOC-NP was detected by SDS-PAGE with expected molecular size of 58 kD and the expression product accounted for 20.34% of the total bacterial protein. The immunological test applying Western blot indicated that SOC-NP fusion protein could react to AIV specifically.