Mycotoxins are toxic secondary metabolites produced by filamentous fungi that grow on grain commodities.They have been widely recognized as the main undesirable substances in grain.A method using liquid chromatography-time of flight mass spectrometry（LC-TOF MS） was developed for simultaneous determination of 13 mycotoxins derived from the fungal genera of Fusarium,Aspergillus and Penicillum in wheat and maize.The samples were extracted with acetonitrile-water-acetic acid （84∶15∶1）,and cleaned up on the Mycosep 226 multifuctional cartridge and the strong anion exchange cartridge.The purified extracts were analysed by LC-TOF MS under the mode of positive electrospray ionization,the mycotoxins were identified by the retention time and the mass accuracy of［M+H］+ or ［M+NH4］+ and quantified in exact mass chromatograms with a mass window width of 10 ppm.The results indicated that 13 mycotoxins had good linear relationships in the certain concentration ranges with their correlation coefficients more than 0.99 and the accurate mass errors less than 5 ppm.The average recoveries of 13 mycotoxins at three spiked levels ranged from 70% to 113% with relative standard deviations of 0.2%-14.5%.The method was suitable for the identification and quantification of targeted mycotoxins at trace level in grain.