Abstract: OBJECTIVE To develop a rapid and sensitive high-performance liquid chromatography-tandem mass spectrometric(LC-MS/MS) assay for the quantitative determination of paracetamol in human plasma, and apply it to a pharmacokinetic and bioequivalence study of two paracetamol formulations in human. METHODS Tinidazole was used as internal standard(IS), paracetamol were extracted from 200 μL human plasma with 1 mL ethyl acetate. Chromatographic separation was achieved on an Waters XBridge^® C₁₈ column under isocratic elution condition. Then with the mass spectrometer operated in positive electrospray ionization mode using multiple reaction monitoring, paracetamol and IS were quantitative analyzed by detecting MS/MS ion transition at m/z 152.0→110.0 and 248.0→121.0, respectively. The validated method was employed in the pharmacokinetic and bioequivalent study of two paracetamol formulations, which conducted in 19 healthy adult human subjects following single-dose oral administrations of 500 mg paracetamol under fasting condition. RESULTS The method showed linearity over the concentration range of 0.1-8.0 μg·mL^-1(r²>0.99) for paracetamol in human plasma. The lower limit of quantitation achieved was 0.1 μg·mL^-1 and the extraction recovery ranged from 91.0% to 98.7%. Intra-and inter-day accuracy were in the ranges of 98.8%-111.3% (precision ≤ 9.0%) and 94.9%-102.6% (precision ≤ 10.7%) respectively. Additionally, in the bioequivalence study, the calculated 90% confidential intervals of geometric mean (test/reference) ratios for pharmacokinetic parameters(C_max, AUC_{0-12 h} and AUC_0-∞) of the two paracetamol formulations were 83.50%-105.79%, 94.25%-101.54% and 93.24%-101.02%, respectively, which all fell within the bioequivalence acceptance range of 80.00%-125.00%. CONCLUSION A rapid and sensitive LC-MS/MS method for the determination of paracetamol in human plasma is developed, it has the characteristics of rapid sensitivity, high recovery and good selectivity and is successfully applied to the pharmacokinetic and bioequivalent study in healthy human subjects. The results show that the test formulation is similar to the reference formulations in terms of rate and extent of absorption, the two formulations are bioequivalent.