Abstract: A method of determination of six synthetic colorants including sunset yellow, lemon yellow, amaranth, carmine, allura red and brilliant blue in dark soy sauce by Ultra Performance Liquid Chromatography Tandem Mass Spectrometry was developed. The sample diluted by water was cleaned up with solid phase extraction polyamide column, analyzed by UPLC/MS/MS. The mobile phase was 0.02mol/L ammonium acetate and methanol in gradient condition. The flow rate was 0.2mL/min. Using the best gradient condition, six synthetic colorants achieved the grate separation in 7min. The condition of tandem mass spectrometer was positive ionization, using the Multiple Reaction Monitoring mode. And all the six synthetic colorants had a good linearity in a concentration range of 10¹000μg/L. The detect limit of the method was 10μg/kg to all six synthetic colorants. The spiked recoveries of six colorants ranged from 80.0% to 93.4%, with the RSDs of 2.4%⁶.8% (n=6) . This method was rapid, showed good accuracy determination, and had a low limit of detection. It showed a satisfied effect of the testing in liquid multiple seasoning like dark soy sauce which had a complex matrix.