Abstract: A study on antifeedant and insecticidal activities of extracts and fractions from Periploca sepium Bunge against Plutella xylostella (L.) was carried out by bioassay-driven separation. The bioassay result showed that antifeedant and insecticidal activity of ethanol extract and chloroform extract was higher than that of petroleum ether extract. The result also indicated that insecticidal components were mainly in benzene partition after the ethanol extract was partitioned by benzene and then by n-butyl alcohol. The benzene partition absorbed on silica gel was transferred to top of the silica gel column, then eluted with petroleum ether, mixtures of petroleum ether and ethyl acetate, ethyl acetate, mixtures of ethyl acetate and methanol and methanol. According to the colors and polarity, 8 fractions were collected, among which fraction 5, 6 and 7 were more active than others. Antifeeding rate and corrected mortality of fraction 5, 6 and 7 were 98.6%~99.8% and 91.5%~100% at the 200 times of dilution, respectively.