04 strains of PRRSV were isolated from pigs infected porcine reproductive and respiratory syndrome virus in provinces as Hung Yen, Dong Nai, Ha Noi, Vinh Phuc is named PR-HY 01, PR - DN 01, PR-HN 01 and PR-VP 01. Their TCID50 respectively is 10-6.9, 10-6.8, 10-6.8, 10.59. Strain PR-HY 01 has been selected as a similary antigenic. Concentration of formalin 0.5 percent could inactivated PRRSV PR-HY 01. Passive antibody in egg yolk belong to hen were immunized PRRSV PR-HY 01 reach highest at week 11th but neutralization antibody appeared at week 4th. Neutralization antibody has been maintained one month in experiment pigs that recommended passive antibody should be injected monthly for prevention porcine reproductive and respiratory syndrome.