Abstract: 1059 serum samples from 40 swine farms of vaccination with PRRSV vaccine and 683 serum samples from 24 swine farms of non-vaccination with PRRSV vaccine were collected to determine antibody level of PRRSV with IDEXX PRRSV antibody ELISA Kit.Positive rate,coefficient variation(CV)and Sample/Positive(S/P)were analyzed.The result showed that in vaccinated pig farms,883 of 1059 serum samples were positive of PRRSV antibody,average positive rate and CV were 83.4% and 67.1,respectively;S/P of 44 serum samples was higher than 2.5,accounting for 4.2%.In non-vaccinated pig farms,290 of 683 serum samples were positive of antibody of PRRSV,average positive rate and CV were 42.5% and 87.4,respectively;S/P of 74 serum samples was higher than 2.5,accounting for 10.1%.The results indicated that non-vaccinated pig farms have been infected by PRRSV.Average positive rate of PRRSV antibody is higher in vaccinated pig farms than in non-vaccinated pig farms.Simultaneously,CV and S/P in vaccinated pig farms decreased obviously compared to non-vaccinated pig farms.It is concluded that vaccination with PRRSV vaccine is one of better ways to control PRRS.