Abstract: A sensitive and selective method for the determination of imidafenacin in human plasma using liquid chromatography combined with mass spectrometry was established, and was applied to the pharmacokinetic and bioequivalence studies of imidafenacin in healthy Chinese volunteers. After the liquid-liquid extraction pretreatment, samples were separated by UPLC on BEH C₈(2. 1 mm×50 mm, 1. 7 μm)column with mobile phase 2 mmol/L ammonium acetate solution with 0. 2% acetic acid and acetonitrile using gradient elution. The mass instrument was operated in the positive ion mode, and the monitored transition was set at m/z 320. 2→238. 1 and m/z 330. 2→248. 2 for imidafenacin and IS(imidafenacin-d10), respectively. In the single-dose, double cycle, self-crossover clinical trial, 24 healthy Chinese volunteers received 0. 1 mg reference or test imidafenacin tablet orally under fasting condition. Drug concentration in plasma was determined by this method and the pharmacokinetic parameters were calculated by DAS 3. 2. 8 software. The linear range of the analysis method is 10. 0 pg/mL to 1 000 pg/mL. The extraction recoveries of the low medium and high concentration samples were 84. 0%, 88. 0% and 90. 0%, respectively. The matrix effects of low medium and high concentration samples were 105%, 100% and 101%, respectively. The pharmacokinetic parameters of imidafenacin for the reference and test tablets were as follows: c_max 524. 8 pg/mL vs 612. 6 pg/mL, t_max 1. 250 h vs 1. 063 h, AUC_0-∞ 2 229 pg ·h/mL vs 2 466 pg ·h/mL. The reference and test tablets of imidafenacin were bioequivalent. This method proved to be rapid and accurate for the pharmacokinetic and bioequivalence studies of imidafenacin.