Nematocidal activity of methanol extracts from the different parts of Clausena lansium was determined by dipping method.The active ingredients were isolated and identified on the basis of active-directed fractionation with column chromatography,thin layer chromatography(TLC),recrystallization and nuclear magnetic resonance(NMR).The results showed that the most effective extract against Bursaphelenchus xylosphilus was seed methanol extract,which gave 100% mortality after 72 h treatment at the mass concentration of 1 mg/mL.The active ingredients were concentrated in petroleum ether fraction and a yellow crystal was obtained and purified.It was identified as Lansiumamide B(N-methyl-N-cis-styryl-cinnamamide) on the basis of NMR data.The bioassay results revealed that LC50 values of Lansiumamide B against B.xylophilus were 8.38,6.36 and 5.38 mg/L after 24,48 and 72 h treatment,respectively.The results indicated that Lansiumamide B was effective against B.xylophilus.