Abstract:When undertaking glucocorticoid risk monitoring missions, the solid phase extraction method was used in the sample pretreatment of two currently valid national standards (Announcement 1031-2—2008 of the Ministry of Agriculture Determination of glucocorticoids residues in animal products by LC-MS/MS method and GB/T 21981—2008 Determination of hormone multiresidues in foodstuffs of animal origin:LC-MS/MS method), led to drawbacks in the testing process, such as intricacies for column purification and time consuming of nitrogen blowing concentration, high testing cost and unfriendly ecological environment and so on. Therefore , on the basis of a large number of experimental studies and practical application tests, the sample pretreatment solid phase extraction through column and nitrogen blowing in the detection of dexamethasone and betamethasone residues in animal tissues was simplified. The method for simultaneous determination of dexamethasone and betamethasone residues in animal tissues(beef liver, beef , pork liver and pork) was developed by ultra-performance liquid chromatography tandem mass spectrometry. Samples were extracted with acetonitrile in the condition of salt fractionation and degreased by hexane. Identification and quantification of dexamethasone and betamethasone were carried out by electrospray ionization in negative mode using multiple-reaction monitoring, and the limits of detection was 0.5μg/kg, limits of quantitation was 1.0μg/kg. There was a good linear relationship between the peak intensity and the mass concentrations within the range of 0.1-50.0μg/L, and the correlation coefficients were good (R2>0.99). The average recoveries of this method for spiked samples in the levels of 1.0μg/kg, 2.0μg/kg and 5.0μg/kg were in the range of 83.3%-98.2%. The research could provide reference for the large-scale detection of residues of this type of drugs in animal tissues in laboratory.