Abstract: The free amino acid contents of cruciferous vegetable Brassica campestris ssp. Chinensis (L.) were studied after treating the vegetable with lambda-cyhalothrin, carbosulfan and azadirachtin by pot experiment. The results showed that at days 2 and 9 after treatment by three pesticides, the total amino acid contents of B. campestris were remarkably higher than that of the control (P<0.01),especially carbosulfan, which caused the content increased by 13.88% compared with that of the control at days 2 after treatment. At days 2 after treatment by lambda-cyhalothrin and carbosulfan, the contents of Glu, Gly and Ala in vegetables increased by 22.29% , 20.60% ,18.83% and 17.87% ,17.87% , 14.58% , respectively, compared with that of the control.The effect of three pesticides on the contents of essential amino acids for human body was marked;the contents increased after treatment by azadirachtin;the contents also increased after treatment by lambda - cyhalothrin and carbosulfan except that of Phe+Tyr and Lys, and the increment was high at early days after treatment. The contents of essential amino acids for insects in vegetables were significantly higher than that of the control (increased by 15.21% and 11.80%, respectively) at days 2 after treatment by lambda-cyhalothrin and carbosulfan.In conclusion, the free amino acid contents in cruciferous vegetable changed significantly after treatment by three pesticides, which suggested that these changes may be related to the pest resurgence after pesticide application.