Abstract: In order to provide guidance for rational application of chlorpyrifos and understand the sublethal effects of chlorpyrifos on Rhopalosiphum padi (Linnaeus), sublethal concentration (LC10, LC20 and LC30) of chlorpyrifos to adults of R.padi were determined by residual film in glass tube, and the sublethal effects on the growth and reproduction of R.padi were evaluated. Results showed that after being exposed to LC10, LC20 and LC30 of chlorpyrifos, the longevity of R.padi adult were (8.60±0.22), (8.03±0.18) and (6.68±0.18)days, respectively, which were significantly shorter than that of the control (10.36±0.31) days; the nymph number per aphid were (21.88±0.63), (20.41±0.53) and (16.68±0.35), respectively, which were significantly less than that of the control (26.40±0.89); the reproductive period were (7.55±0.220), (6.69±0.17) and (5.64±0.15) days, respectively, which were significantly shorter than that of the control (9.13±0.31) days. The duration of nymph of R.padi offspring was not affected significantly when the adult was exposed to sublethal concentration of chlorpyrifos. LC30 of chlorpyrifos could inhibit the offspring fecundity, the number of nymph per aphid decreased by 3.74 and reproductive period shortened by 1.39 days as compared with that of the control. The demographic growth parameters showed that the net reproductive rate(R0) of R.padi decreased by 34.71% and population doubling time(t) prolonged by 17.37% after exposure to LC30 of chlorpyrifos;the mean generation time(T)increased by 12.59% after exposure to LC20 of chlorpyrifos; no significant difference was observed between the parameters of LC10-treatment and control. The results that chlorpyrifos could reduce the longevity and reproduction of R.padi adult at sublethal concentration will be helpful in developing strategies for the IPM of R.padi.