A method for determination of residues of 26 β2-agonists in pork liver was developed using high performance liquid chromatography with tandem mass spectrometric ( HPLC-MS/MS ) . After enzymatic hydrolysis with β-Glucuronidase/Arylsulfatase for 12 hours, the pH of sample solution was adjusted to 1 using perchloric acid for protein precipitation. The precipitate was extracted with 0. 1mol/L perchloric acid aqueous. The extracts in the above two steps were combined and adjusted to pH 4 for the solid phase extraction ( MCX) . And then the 26 β2-agonists residues in the extracts were separated on a reversed phase HPLC column using a gradient elution program of 0. 1% formic acid aqueous solution (A) and 0. 1% formic acid in acetonitrile solution ( B) . Multiple reaction monitoring ( MRM) with positive polarity was selected to monitor qualitative and quantitative ion. Based on the optimized method, 26 β2-agonists could be analyzed in 15 min. The recoveries ranged from 64 . 0% to 112 . 7% for the 26 kinds ofβ2-agonists residues with three spiked levels of 5, 10 and 20 μg/kg. The relative standard deviations ( RSDs) were less than 15. 2%. The limits of detection (LOD) for the 26 kinds of β2-agonists were 0. 15-1. 35 μg/kg.