Abstract: A method for the determination of bongkrekic acid in fermented corn flour by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) with QuEChERS purification was proposed. The sample (2.0 g) was taken, and 10 mL of water was added, and the mixture was swirled for 1 min. Then 10 mL of acetonitrile solution containing 5% (volume fraction) acetic acid was added, and the mixed solution was swirled for 1 min. Then 6.0 g of anhydrous magnesium sulfate and 1.5 g of anhydrous sodium acetate were added, and the mixture was swirled for 1 min and centrifuged for 5 min. The supernatant (5 mL) was taken, and placed into a 15 mL-centrifuge tube preloaded with 200 mg of C₁₈ and 900 mg of anhydrous magnesium sulfate, and the mixture was swirled for 1 min. The supernatant (2 mL) was taken and blown to dryness by nitrogen at 40 ℃, then the residue was redissolved with 1 mL of 50% (volume fraction) acetonitrile solution. After vortex for 1 min, the above solution was filtered with 0.22 μm nylon filter membrane, and then tested by HPLC-MS/MS. In the chromatographic analysis, the mixed solution composed of 0.1% (volume fraction) formic acid solution and methanol at different volume ratios was used as mobile phase for gradient elution. In the mass spectrometry analysis, the electrospray ion source with negative mode was used for ionization, and the multi-reaction monitoring mode was used for detection. The matrix matching standard solutions were used to draw the working curve, with external standard method for quantification. As shown by the results, the linear range of the working curve was 1-200 μg·L^-1, with detection limit of 0.75 μg·kg^-1. At 5 spiked concentration levels, the recoveries were in the range of 78.9%-112%, and RSDs (n=6) of the determined values were in the range of 4.2%-16%.