Abstract: A method was developed for the simultaneous determination of 11 pesticides in drinking water, including dimethoate, carbofuran, dichlorvos, atrazine, parathion-methyl, malathion, parathion, Bentazone, chlorpyrifos, 2, 4-D and deltamethrin by liquid chromatography tandem mass spectrometry (LCMSMS). The sample was directly filtered by filter membrane, then eluted by gradient elution on ZORBAX Eclipse Plus C18 column (2.1*100 mm, 1.8 μm), detected by multiple reaction monitoring mode (MRM), and quantified by external standard method. The results showed that the linear correlation coefficients of 11 pesticides were all above 0.99, and the linearity was good. The method detection limits were 0.05 μg /L to 1.04 μg /L, The recoveries were 83.2% to 104%, and the RSDs were 0.9% to 5.3%. The method can detect all the target compounds at the same time with one injection, and it only takes 6 minutes to complete the detection of a single sample. It has high sensitivity, good reproducibility, high efficiency and simple pretreatment, and is suitable for the daily detection of 11 pesticides in drinking water.