Abstract: High performance liquid chromatography in hyphenation with tandem mass spectrometry (HPLC-MS/MS) was applied to the determination of residual amounts of 4 kinds of β-agonists,including celenbuterol,salbutamol,raotopamine and terbutalin in foodstuffs.The sample was extracted with ammonium acetate buffer solution,which was concentrated and purified by LC-18 Sep Pak and LC-SCX Sep Pak solid-phase extraction column.The eluate was evaporated to near dryness and diluted to a definite volume with acetonitrile-H2O(10+90) solution,and separated on the C18 column.The eluate was used for tandem MS analysis.External standard calibration of isotope was adopted in the determination.Linear relationships between values of peak area and mass concentration of celenbuterol,raotopamine,salbutamol and terbutalin were obtained,with their detection limits of 0.05,0.1,0.1,0.1 μg·kg-1 respectively.Values of recovery of celenbuterol,salbutamol,raotopamine and terbutalin in the range of 91.8%-99.0%,98.3%-105.5%,76.8%-82.8% and 75.1%-85.2% were found respectively in a sample pig liver.Values of RSD′s (n=7) found were less than 12.5%.