Objecave To develop a sensitive and specific LC-MS/MS method for determination of testolactone in humanurine.Methods A C_(18 )column(2.1×50mm,3.5μm) was used.The mobile phase Was a mixture of acetonitrile and the buffersolution(ammoniumacetate-watersolution adjusted with formic acid to pH 3.5)at a flow rate of 0.5ml/min.A mass spectrometer equipped with electrospray ionization source was used as a detector and operated in the positive mode.In multiple reaction monitoring(MRM)mode,the ion transitions of m/z 301→121 and m/z 301→25 was used to qualify and quantify the testolactone,respectively.Results Chromatograms showed no endogenous interfering peaks with the urine blank sample.Each analysis was completed within 7min The calibration wag linear in the concentration range within 0.1~50μg/ml.The intra-batch and inter-batch RSD were less than 10%.The recovery rate of the extraction was about 60%.Conclusions The method is proved to meet the requirements of WADA and be suitable for routine screening.