Abstract: In order to understand the prevalence of porcine reproductive and respiratory syndrome （PRRS） in eastern regions of Heilongjiang Province, 663 samples of porcine serum were collected from Mudanjiang City, Ning′an City, Hailin City, Suifenhe City, Jixi City, Jidong City, Jiamusi City, Mishan City, Hulin and other eastern regions of Heilongjiang Province. And the serum samples were from boar, sow, piglets and fattening pigs. And the pig farms included large-scale pig farms, small-scale pig farms and scatter-fed household. The serological investigation on the prevalence of PRRS in eastern regions of Heilongjiang Province was made by using ELISA. The results showed that the detection results of serum samples from 134 pigs were positive among 663 serum samples and the positive rate reached 20.21%.529 pigs were negative and the negative rate was 79.79%.S/P ratio of 26 pigs was more than 2.0, which took 19.40%of total positive ratio.