Nematictdal activities of two alkaloids ,aloperine and Δ 11 dehydroaloperine identified by GC-MS and separated by preparative HPLC,were assayed with the immersion bioassay. Results showed that aloperine containing >N H functional group in its structure displayed much stronger nematicidal activity than Δ 11 dehydroaloperine with >N moiety. The results provided new proof for the hypothesis proposed by Zhao Bo guang on the relationship between molecular structures of quinolizidine alkaloids and their nematicidal activities.