In order to evaluate the safety of dimethomorph and cyazofamid in cucumber and soil，a high performance liquid chromatography-tandem mass spectrometry（HPLC-MS/MS） was developed for the simultaneous detection of dimethomorph，cyazofamid and its metabolite，4-chloro-5-p-tolylimidazole-2-carbonitrile（CCIM） in cucumber and soil.Samples were extracted with acetonitrile，cleaned up with PSA and C18，and then analyzed by HPLC-MS/MS in multiple reaction monitoring（MRM） mode with the matrix matched calibrations method.There existed good linearities for All analytes in the range of 0.01- 0.5 mg/L with their correlation coefficients（r） more than 0.994 0.At three spiked levels of 0.05，0.1 and 0.5 mg/kg，the recoveries for dimethomorph，cyazofamid and CCIM in cucumber and soil were in the range of 78%-105%with relative standard deviations（RSDs） of 1.3%-14.8%.The limit of quantitation was 0.05 mg/kg.Residues and dissipation of dimethomorph and cyazofamid in cucumber and soil were investigated.The half lives of dimethomorph in cucumber and soil were 1.2-2.1 d and 3.0-9.6 d，respectively，and the half lives of cyazofamid and CCIM in cucumber and soil were 0.9-2.3 d and 1.8-6.2 d，respectively.The method is simple，rapid，sensitive and accurate，and could meet the requirements for detection of dimethomorph，cyazofamid and CCIM residues in cucumber and soil.