An automatic analysis method was developed for the determination of 16 β-agonists residues including orciprenaline,clorprenaline,cimaterol,terbutaline,tulobuterol,cimbuterol,salbutamol,zilpaterol,clenbuterol,ractopamine,fenoterol,mabuterol,bromochlorobuterol,mapenterol,phenylethanolamine A and brombuterol in pig urine by liquid chromatography-tandem mass spectrometry(LC-MS/MS).The sample was digested overnight at 37 ℃, and purified by turboflow online cation solid-phase exaction(online-MCX-SPE)at a flow rate of 3 mL/min.The elution was selected with 5% ammonium in methanol-water(9∶1).The separation of 16 compounds was carried out on a CAPCELL MGⅡ chromatographic column,using 0.1% formic acid methanol-01% formic acid solution containing 5 mmol/L ammonium formate as mobile phase,and determined in positive electro-spray ionization mode.Under the optimized conditions,the calibration curves of 16 agonists were linear in the concentration range of 0.01-50 μg/L with correlation coefficients(r2) not less than 0.998 3.The limits of detection(LOD) were in the range of 0.01- 0.025 μg/L and the limits of quantitation(LOQ)were 0.025-0.10 μg/L.The recoveries of the method ranged from 62.4% to 117.1% with relative standard deviations(RSDs)of 3.9%-16.3%.The determination of 213 pig urines demonstrated that the method was simple and automatic,and was suitable for the quick confirmation of 16 β agonists in large batch of pig urines.