The effect of pesticide residues on the nutritional quality of pakchoi has been studied by applying low, medium and high concentrations of pesticides (chlorothalonil, chlorpyrifos and fipronil) to pakchoi. The effects of different washing and cooking methods on removing pesticide residues in pakchoi were compared. The results showed that the contents of water, soluble protein and nitrate all decreased firstly and then increased with the increase of the application concentration; there were no significant differences in vitamin C contents and carotenoid contents between the different treatment groups(P> 0.05); the contents of reduced sugar, calcium and phosphorus increased firstly and then decreased compared with the blank group; the crude fiber content of high concentration group increased. Detergent had the best removal effect for all the three pesticides, alkali water and rice washing water soaking was the second, and salt water and clear water was the last. The thermal stability of chlorothalonil is poor, and the removal percentages of three cooking methods for chlorothalonil were all above 94%; 60℃ blanching and 100℃ boiling for chlorpyrifos had lower removal effect, while hot oil stir-frying could significantly improve the removal effect; the removal effect of stir-frying was the best for fipronil, followed by blanching and boiling.