A highly sensitive and rapid liquid chromatography-tandem mass spectrometry method was developed for the determination of clinofibrate in human urine.The analyte and IS were extracted through a simple protein precipitation by the mixture of acetonitrile and 1 mol/L hydrochloric acid (95:5,v/v) and separated on an Inspire C18 (150 mm×4.6 mm I.D.,5μm particle size) column using isocratic elution with methanol and water containing 0.1 % formic acid and 10mM ammonium acetate (90:10,v/v).Mass spectrometric detection was performed in electrospray positive ionization MRM mode.The mass transition was m/z 486.3→175.0 for clinofibrate and m/z 361.1→233.1 for IS,respectively.The flow rate was 0.6 mL/min and the column oven temperature was set at 35 ℃.The total run time was 6.5 min.Good linear relationships were obtained for all analytes over the concentrations ranging of 0.1002-10.02 μg/mL (r2=0.9991) and the limit of quantification was 0.1002 μg/mL.The extraction recovery was larger than 87.4% and intra- and inter-batch precision and accuracy with RSD were all less than 6.5%.The total amount of unchanged clinofibrate excreted in urine was about 0.34 %.This method was successfully applied to the pharmacokinetic study of clinofibrate in human urine.