High pathogenic-porcine reproductive and respiratory syndrome (HP-PRRS) has caused great economic losses to pig industry in China. In order to study the changes of serum viremia and body weight gain in pigs after HP-PRRSV (HP-PRRS Virus) infection,72 healthy piglets from a large white pigs and Tongcheng pigs crossed population were selected and infected with HP-PRRSV. The clinical symptoms were observed,weight was measured,blood samples were collected,serum was separated and viremia was measured on 0,4,7,11,14,21,28,35 dpi (days post infection). The results showed that the growth rate of body weight was slow at 4 dpi,the body weight increased negatively from 4 to 21 dpi,the loss of weight reached the maximum from 7 to 11 dpi,the body weight increased positively and the growth increased gradually from 21 to 35 dpi. Viremia peaked on 4 dpi and lasted until 7 dpi,and decreased to 6.62 log10 copies/mL from 7 dpi to 35 dpi. Death occurred from 7 dpi,and the dead individuals were mainly concentrated from 7 to 14 dpi. The death peak appeared on 10 dpi,and the number of dead individuals was basically stable after 19 dpi. According to the survival on 14 dpi,the pigs were divided into two groups:disease-resistant and susceptible group. The viremia of the disease-resistant group was significantly lower than that in the susceptible group on 4,7,11 dpi (P<0.05),and the weight gain of the disease-resistant group was significantly higher than that of the susceptible group on 4-7 dpi,7-11 dpi,and 11-14 dpi (P<0.05). The above results suggested that body weight gain and viremia could be used as indicators to predict the resistance of PRRS.