An analytical method was established for the simultaneous determination of 17 pesticide residues in flour by ultra performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry(UPLC-Q-TOF/MS).The QuEChERS method was validated for the extraction.In this method,the samples were extracted with 0.1%(by volume)acetic acid-acetonitrile solution,and cleaned-up by PSA and C18 adsorbents,then determined by UPLC-Q-TOF/MS with electrospray ionization in positive mode.The quantification analysis was performed by the external standard calibration.A database including accurate mass and fragment ions information was established.The correlation coefficients(r)were more than 0.995 in the linear range of the 17 pesticides.The limits of quantitation(LOQs)of the method were in the range of 5.0-10.0 μg/kg.The recoveries at three spiked levels were between 70.3%and 114.9%with relative standard deviations(RSDs,n=6)of 0.4%- 11.7%.With the advantages of simplicity and good stability,the method is available for practical application.