Abstract: According to the genome sequences of the duck NDV,apair of specific primers was designed.The NP gene of the virus was amplified by RT-PCR and cloned into the prokaryotic expression vector pET-30 a.The recombinant plasmids were transformed into BL21(DE3)E.coli.Subsequently,this recombinant fusion protein was successfully expressed following IPTG induction.SDS-PAGE showed that the protein had an approximate molecular weight of 59 kD,and the Western blotting assay revealed that it could be recognized by the monoclonal antibody against histidine-tagged protein.The antiserum was,then,produced by the immunized ICR mice with the recombinant protein.Western blotting on the antiserum indicated its specific reactivity with NDV allantoic fluid.It was concluded that the NP gene could be successfully expressed in E.coli,and the antiserum could be used for detection of NPprotein.