β-Agonists　have　been　abused　as　the　growth-promoting　agent　in　food-producing　animals　over　20　years.　The　proof　of　using　illegal　drugs　in　food,　which　is　necessary　for　a　regulatory　action,　usually　requires　a　high　degree　of　specificity　and　sensitivity.　This　paper　reported　an　ultra-high　performance　liquid　chromatography　(UHPLC)-ESI/MS/MS　method　for　the　confirmation　of　multi-residues　of　the　13　β-agonist　compounds　in　milk.　A　wide　range　of　analytes　related　to　β-agonists　(brombuterol,　cimaterol,　clenbuterol,　clenpenterol,　clorprenaline,　hydroxymethylclenbuterol,　isoxsuprine,　mabuterol,　ractopamine,　ritodrine,　salbutamol,　terbutaline,　tulobuterol)　with　similar　chemical　structures　was　investigated　in　order　to　demonstrate　the　applicability　of　our　method.　This　method　consists　of　a　two-step　extraction　and　a　MCX　SPE　cleanup.　The　final　extract　was　separated　by　UHPLC　within　5　min　and　then　injected　in　an　electrospray　ionization　mass　spectrometry　for　the　determination.　Using　clenbuterol-D9,　salbutamol-D3,　and　ractopamine-D5　as　internal　standards,　and　accomplishing　with　the　matrix　matched　calibration　curves　to　compensate　for　the　matrix　effects,　the　quantitative　data　showed　good　linear　response　within　the　concentration　ranges　studied.　The　detection　limits　(CCα)　and　detection　capabilities　(CCβ)　of　the　analytes　were　found　in　the　range　of　0.01-0.16　μg/L　and　0.03-0.21　μg/L,　respectively.　Recoveries　of　the　compounds　were　found　from　82.5%　to　101%　at　the　spiked　level　of　0.05-2.5　μg/L,　and　the　relative　standard　deviation　was　within　the　range　of　7.17%　and　16.4%.　Furthermore,　an　inter-laboratory　study　among　eight　laboratories　was　conducted　to　further　validate　the　method,　and　the　results　were　found　satisfactory.　©　2011　Springer　Science+Business　Media,　LLC.