Abstract: The present experiment was performed with the objective of establishing an indirect ELISA for detection of PRRSV with the purified NSP2 fusion protein as coating antigen. The major antigen region of NSP2 was successfully amplified by RT-PCR from a highly pathogenic PRRSV (SCMS08 strain), and inserted into pET-32a(+) vector. The recombinant plasmid was transformed into E. coli Rosetta 2 (DE3) and induced with IPTG. The fusion protein was treated with Ni-chelated chromatography under denaturing conditions. With the purified fusion protein as coating antigen, an ELISA for detection of PRRSV was established. SDS-PAGE showed that the fusion protein was expressed at high level in Rosetta 2. Western blot analyses showed that the expressed protein was recognized specifically by anti-His monoclonal antibody as well as PRRSV positive serum. In the optimized NSP2-ELISA, the fusion protein was coated at 1.7 μg·mL^-1 and swine serum samples were diluted at 1∶40. About 185 serum samples were detected by the method and IDEXX-ELISA kit, respectively. The agreement ratio between the two methods reached at 90.8%. The results indicated that NSP2-ELISA was specific, sensitive and suitable for routine diagnosis of PRRS and also for epidemiological surveys.