The invention discloses a method for simultaneously detecting multiple fungaltoxins in grains. The method comprises the steps of extracting a grain sample to be detected through an acetonitrile-water solution containing acid, salting out, purifying, centrifuging, and membrane filtering to obtain sample analytic liquid; utilizing an ultra-high performance liquid chromatography-tandem mass spectrometry for simultaneously detecting the multiple fungaltoxins. According to the method provided by the invention, the fungaltoxins are subjected to qualitation and quantitation by adopting a multi-reaction monitoring mode (MRM). After the grains are subjected to pretreatment, the ultra-high performance liquid chromatography-tandem mass spectrometry is utilized for simultaneously detecting extracted 10 fungaltoxins. The sample is extracted through the acetonitrile-water solution with a certain concentration and containing the acid, a sample extracting solution is salted out and purified, and the multi-reaction monitoring mode of the high performance liquid chromatography-tandem mass spectrometry is utilized for detecting, so that the defection efficiency is improved, the detection cost is rediced, the sensitivity is high, the repeatability is good, and the adding standard recovery is high.