Abstract: Nonstructural protein 1(NS1)from the avian Tembusu virus were amplified and expressed in E.colito establish ELISA procedures for the detection of antibodies in the virus.Biological activity of the expressed protein was analyzed by using SDS-PAGE and western blot.The results indicated that the recombinant NS1 with a molecular weight of 60 kD was expressed in high level with good biological activity.It was subsequently used to establish an indirect ELISA for the detection of antibodies in the virus.The optimized procedures included the uses of 2.5μg·mL^-1 recombination protein,1∶100serum dilution,and the goat anti-duck IgG conjugate(1∶3000).Although the NS1-ELISA showed desirable specificity and repeatability,it failed to effectively differentiate the inactivated Tembusu vaccine serumfrom the naturally infected serum.Thus,this method could not be applied as a diagnosis tool for Tembusu virus.