Abstract: The NSP2 gene fragments of porcine reproductive and respiratory syndrome virus (PRRSV) were amplified by RTPCR from the extracted RNA samples of Culex tritaeniorhynchus collected from 3 infected pig farms， and then were cloned into pMD-18T vector for sequence analysis. And the homogenate supernatant of Culex tritaeniorhynchus samples were inoculated to the Marc-145 cells for isolation and identification of PRRSV. The results showed that the specific DNA fragments of about 1 060 bp were amplified from the RNA samples from Culex tritaeniorhynchus， and the sequences of these fragments shared high homology with the NSP2 gene of PRRSV isolates from infected pigs in the same farm. And there are 90 nucleotides deletion in NSP2 gene compared with CH-1a strain of PRRSV. The obvious cytopathic effect were appeared in Marc-145 cells inoculated with the samples of Culex tritaeniorhynchus， and the specific fluorescence were observed in the infected cells by indirect immunofluorescent assay， and the PRRSV-N gene fragments were amplified by RT-PCR from infected cells. These results indicated there are PRRSV in Culex tritaeniorhynchus， and it could be an important way of prevalence and transmission of PRRS.