Abstract: Feeding inhibition and toxicity of the extracts from the six plants: Melia azedarach Linn., M. toosenelen Sieb. et Zncc., Gleditschia sinensis Lam, Hibiscus syriscus Linn., Albizia julibrissin Durazz., and Sophora alopecuroides Linn. on the caterpillars of Dendrolimaus puctatus Walker were examined by the bioassay. It was found that the extracts of A. julibrissin and H. syriscus did not affect caterpillars’ feeding significantly and showed no toxicity to the caterpillars. The alcohol extracts of G. sinensis inhibited caterpillars’ feeding. but showed no toxicily to them. The petroleum ether extracts of M. azedarach and M. toosenelen and the alcohol extracts of M. toosenelen inhibited caterpillars’ feding and showed toxicity to them at higher concentrations. The water solvable parts of the total alkaloids of S. alopecuroides inhibited cateripllars’ feeding significantly. The water solvable alkaloids, matrine, N-oxymatrine, sophoridine, cytisine, aloperine showed feeding inhibition and toxicity to caterpillars at different levels. Among them, N-oxymatrine and sophoridine showed stronger effects of feeding inhibition, sophoridine and aloperine showed higher toxicity to caterpillars.