Three extraction solvents such as ammonium acetate solution（used in No.1025-18-2008 Bulletin of the Ministry of Agriculture）,acetonitrile and acetonitrile-10% sodium carbonate solution were used to extract nine β-agonists residues in pig liver,respectively,and the extraction efficiencies of targeted compounds were compared.The experimental results revealed that the recovery of penbutolol increased to 79% and that for fenoterol was 32% when using acetonitrile as extraction solvent.The recoveries of the eight drugs（ractopamine,clenbuterol,salbutamol,terbutaline,cimaterol,clorprenaline,tulobuterol and penbutolol） were more than 80% except that 72% of recovery for fenoterol when using acetonitrile-10% sodium carbonate as extraction solvent.A liquid chromatography-tandem mass spectrometric method was established for the simultaneous determination of nine β-agonists residues in pig liver.Under the optimal conditions,the linear ranges of nine analytes were between 0.50 μg/kg and 25 μg/kg with correlation coefficients（r） more than 0.99.At the spiked levels of 0.50,2.0,10 μg/kg,the mean recoveries of nine β-agonists in pig liver ranged from 71% to 105%,with intra- and inter-RSD less than 15%.All the detection limits of nine β-agonists were 0.2 μg/kg.The method could meet the requirements for residue analysis on accuracy and precision.