Objective To develop an ultrahigh-performance liquid chromatography-tandem mass spectrometry （UHPLC-MS/MS） analytical method for the determination of cyanuric acid in the outer packaging of imported cold-chain food.Methods A 50% aqueous acetonitrile solution was used as an extraction solvent. The extraction was performed by shaking the samples. The sample was centrifuged， and the supernatant was transferred for injection. Cyanuric acid was separated using a Waters ACQUITY BEH HILIC （2.1×100 mm， 1.7 μm）. The mobile phase consisted of acetonitrile and a 10 mmol/L aqueous ammonium acetate solution. An isocratic elution was also performed. Cyanuric acid was detected using UHPLC-MS/MS.Results Good linearity was achieved， with a correlation coefficient above 0.999 0. The limit of detection and limit of quantitation of the method were 5.0-20.0 and 20.0-50.0 μg/kg， respectively. The mean recoveries at low， middle， and high spiked levels were 80.0%-96.6%. The intra- and inter-day relative standard deviations were <12.3%.Conclusion Due to its straightforward sample preparation， reliable recovery， heightened sensitivity， and precision， the established method has been proven suitable for the assessment of cyanuric acid in the outer packaging of imported cold-chain food.