Abstract: The contact toxicity of chloroform extracts of Brucea javanica (L.) Merr., Annona squamosa L. and Gelsemium elegans Benth to Pteromalus puparum L. were evaluated in laboratory by the method of dry film bioassay, and influence of the plant extracts on the parasitism of the wasp was also tested, with the chemical pesticide beta-cypermethrin as control. Results showed that the three plant extracts were safe to P. puparum and did not affect its parasitic effect. The mortality of the wasp 24 h after being treated with the three plant extracts were 13.2%, 8.2% and 2.0%, respectively. Beta-cypermethrin had significant contact toxicity to the wasp and the mortality reached 100% 3 h after treatment. Beta-cypermethrin also reduced the wasp's ability to parasitize host pupae, rate of treated host pupae from which wasps emerged was only one sixth of that of plant-extracts treated pupae.