Abstract: Based on the bioassay and field investigation, toxicity of dichlovos, beta-cypermethrin and abameetin to larvae of Plutella xylostella collected from different cruciferous vegetable types were tested, and the influence of abameetin on their population dynamic were also carried out. It shows different insecticides exhibited different toxicity to P. xylostella larvae collected from different hosts. Compared with 2003，dichlovos didn’t show significant discrimination to P. xylostella larvae collected from B. oleracea in 2004，while showed a significant higher toxicity in 2005 than in 2003. Only in 2005, P. xylostella from B. oleracea showed more susceptible to dichlovos than from B. chinensis. Beta-cypermethrin showed no significant difference in susceptibility to P. xylostella larvae collected from B. oleracea among three years, but showed higher toxicity to larvae from B. chinensis in 2005 than those in 2003. Abameetin caused significantly higher LC50 to larvae form B. oleracea in 2003 than those in 2005 while there was no difference between 2003 and 2004. In three years investigated, abameetin didn’t lead to the LC50 difference between larvae from two hosts. Population dynamic in two host fields were similar with lower larvae amount in B. chinensis. Fields treated with abameetin for 1 time could attribute to about half lower peak of P. xylostella larvae than control field. There were no significant peak in the fields treated with with abameetin for 2 time.