Abstract: To clarify the safety of malathion in cabbage mustard and flowering Chinese cabbage, the residue of malathion in the two kinds of vegetables was studied. A gas chromatography tandem mass spectrometry (GC/ MS) method was developed for the determination of malathion. Samples were extracted by acetonitrile, purified by QuEChERS purification package, filtered by 0.22 μm membrane, separated by gas chromatography column (TG-5SILMS 30 m×0.25 mm, 0.25 μm), and detected by selected reaction monitoring mode (SRM). The linear relationship was good in the range of 0.5-100 μg/L, the correlation coefficient r was above 0.999. The limit of detection (LODs) was 0.3 μg/kg, and the limit of quantitation (LOQs) was 1 μg/kg. The adding concentration was at 3 levels of 2, 20 and 200 μg/kg, the average recoveries of malathion varied from 89.9% to 120.6%, the relative standard deviations (RSD) was less than 5. 200 batches of cabbage mustard were detected by this method, and malathion residue was not detected. 200 batches of flowering Chinese cabbage were tested, and malathion residue was detected in 2 batches, the detection rate was 1%. The method passed the acute dietary risk assessment, the risk entropy (HQ) is less than 1, and the dietary intake is safe.