An analytical method was developed for the determination of sulbactam in milk using hydrophilic interaction chromatography tandem mass spectrometry（HILIC-MS/MS）.The samples were extracted with 0.2% acetic acid solution，then purified and enriched with an HLB solid-phase extraction（SPE）cartridge.The separation of sulbactam was carried out on an Acquity UPLC BEH HILIC column using ammonium formate - acetonitrile as mobile phase．The quantitation analysis of target compound was performed under the multiple reaction monitoring（MRM） mode by the external standard method.A good linear relationship was obtained between peak area and concentrations of sulbactam in the range of 1-100 μg/L，with correlation coefficients more than 0.99 and limit of quantitation（LOQ） of 1.0 μg/kg．The recoveries at spiked levels of 1.0-50.0 μg/kg ranged from 82% to 102% with relative standard deviations of 1.6%-47%.With the advantages of convenience，sensitivity，good recovery and repeatability，the method was suitable for the detection of sulbactam in milk．