Abstract: Toxicity of ethanol extracts of thirty-six traditional Chinese medicinal (TCM) herbs to adult nematodes and eggs of Bursaphelenchus xylophilus were evaluated in this study to find efficient nematicidal compounds. Bioassay results showed that the ethanol extracts of Cortex moutan radicis, Coptis chinensis franch and Radix et rhizomarhei possessed excellent efficacy with 100% mortality of adults, less than 20% egg hatching rate and more than 60% mortality of eggs at the concentration of 10 g/L. The LC₅₀ of ethanol extracts of three TCM herbs were 1.81, 0.2638 and 1.07 g/L respectively against B. xylophilus after treatment of 72 h. Preliminary separation of active ingredients of three TCM herbs using ethyl acetate and water was employed to examine the nematicide activities of the extracts. The active ingredients of C. moutan radicis presented in ethyl acetate extract, while the active ingredients of C. chinensis franch and R. et rhizomarhei presented in water extracts. The LC₅₀ of active ingredients from three TCM herbs were 0.712, 2.370 and 0.067 g/L respectively against B. xylophilus after treatment of 72 h. This research will provide a theoretical basis for the development of novel biorational nematicide.