Abstract: Objective: By simulating the heating process of edible oil in daily life, the transformation and degradation conditions of tert butyl hydroquinone (TBHQ) in vegetable oil samples containing TBHQ were determined. The two transformation products of TBHQ, tert butyl p-benzoquinone (TQ) and 2,5-di-tert-butyl-1,4-benzoquinone (TBK), were finally determined by gas chromatography-mass spectrometry and matching of unknown compounds with the database. And a gas chromatography-mass spectrometry (GC-MS) method was developed for the determination of tert-Butyl-hydroquinone (TBHQ) and its two degradation products 2-tert-Butyl-1,4-benzoquinone (TQ) and 2,5-di-tert-butyl-1,4-benzoquinone (TBK) in vegetableoil. Methods: The sample was dissolved in n-hexane saturated with acetonitrile and extracted with acetonitrile saturated with n-hexane. The acetonitrile layer was extracted twice, and the acetonitrile layer was combined. The acetonitrile layer was concentrated to nearly dry in 40 ℃ water bath and then redissolved with methanol, HP-5MS UI capillary column (30 m×0.25 mm, 0.25 μm) was used without splitter injection. Then selected the ion monitoring mode, gas chromatography-mass spectrometry determination, external standard method quantitative. Results: The linear range of the three compounds was good (R²>0.995). Under the three levels of concentration, the recoveries were 83.40%~107.71%, and the relative standard deviation (n=6) was less than 8.5%. The limits of quantitation (loqs) of TBHQ and TBK were 10 μg/kg and TQ was 50 μg/kg. 25 batches of samples were measured. TQ was measured in two batches of samples, and TBK was measured after heating treatment. Conclusion: The method is simple, sensitive, accurate and reliable. It is suitable for the simultaneous determination of TBHQ and its degradation products in vegetable oil.