Abstract: A sensitive and efficient method was developed for the simultaneous determination of six azo-dyes (Chrysoidin, Para Red, Sudan I, SudanⅡ, SudanⅢ and Sudan Ⅳ) in soybean products using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The samples were extracted with a simple procedure using acetonitrile. The supernatant was directly analyzed by LC-MS/MS after centrifugation. The sample was separated on a Waters XTerra C18 column, and detected by MS/MS with the multiple reaction monitoring (MRM) mode. Matrix calibration was used for quantitative testing of the method. Good linearity is obtained over the range of 2-100 μg/L with a correlation coefficient R²>0.99. The recoveries are 93.9%-110.6% with good coefficients of variation of 3.1%-14.8%. Limit of detection (LOD) and limit of quantification (LOQ) for the six dyes are in the ranges of 0.03-0.75 μg/kg and 0.1-2.0 μg/kg, respectively. This method has been applied successfully for the determination of the six azo dyes in soybean products.