HP-PRRSV has caused great economic losses to pig industry in China. In order to study the changes of viremia in serum and body weight after HP-PRRSV infection,72 healthy piglets selected from a large white pigs and Tongcheng pigs crossed population were infected with HP-PRRSV. The clinical symptoms were observed,the blood samples were collected and weight was measured on 0 4, 7, 11, 14, 21, 28 and 35 day post infection(dpi),serum was separated and viremia was measured. The results showed that the growth rate of body weight was slow from 0 to 4dpi,the body weight increased negatively from 4 to 21dpi, the loss of weight reached the maximum from 7 to 11dpi,the body weight increased positively and the growth increased gradually 21 to 35dpi.Viremia increased from 0 to 4dpi, peaked on 4dpi and lasted until 7dpi ,viremia decreased to 6.62log10 copies/mL from 7dpi to 35dpi.Death occurred 7dpi, and the dead individuals were mainly concentrated on 7 to 14 dpi. The death peak appeared on the 10dpi, and the number of dead individual was basically stable 19dpi.According to the survival or not death on 14dpi, the pigs were divided into two groups: resistance and susceptibility,the viremia of resistance was significantly lower than susceptibility 4,7,11dpi(p<0.05),the weight gain of resistance was significantly higher than that of susceptibility at 4-7dpi,7-11dpi,11-14dpi(p< 0.05).The above results showed that the weight gain and viremia could be used as indicators to predict the resistance of PRRS.