The shift of virulence in ASD7 of rice brown planthopper from field and laboratory was studied. The results showed that the field populations with different virulence, of which the virulence was determined by the amount of honeydew excreted on ASD7, can shift to ASD7 population after rearing four generations on ASD7 respectively. On the contrary, the virulence of ASD7 population became weak gradually during rearing on TN1. After seven generations rearing on TN1, ASD7 population degenerated into TN1 population. It is suggested that virulence of rice brown planthopper was variable and the character of variety resistant or susceptible to insect was the exterior factor of virulent shift.