Abstract: A stable isotope dilution mass spectrometry technology for determination of urotropine in bean curd sticks by liquid chromatography with tandem mass spectrometry was developed.Isotopic urotropine was added to bean curd sticks as internal standard,and extracted with acetonitrile.Solid phase extraction( SPE) was applied to purify the sample.The separation was performed on a HILIC column. The analyte was determined by multiple reaction monitoring( MRM) mode with UPLC- MS / MS,and quantified by the internal standard method.The method showed good linear relationship in the range of 1⁴0 μg / L for urotropine,the correlation coefficient square was 0.9996.The limit of quantitation( LOQ) for sample was 2 μg / kg.The average recoveries were 97.8% ¹01.5% at spiked levels of2,10,30 μg / kg.The relative standard deviation( RSD,n = 6) was 1.9% ⁴.8%.This method is sensitive,accurate and reproducible.It is suitable for monitoring illegally added urotropine in bean curd sticks.