Abstract A fast and sensitive method to quantify fasudil hydrochloride (FH) and its active metabolite hydroxyfasudil (M3) in human plasma using HPLC–MS/MS has been developed and validated in present study. The method involved simple sample preparation with methanol as protein precipitation (3:1, v/v) and ranitidine as an internal standard (IS). The analytes and IS were separated using a gradient elution procedure on the analytical column ZORBAX StableBond-C18 (5 μm, 150 mm × 4.6 mm). Detection was performed by an AB 3200 QTRAP tandem mass spectrometer equipped with a Turbo IonSpray ionization source set in positive ion mode. Multiple reaction monitoring (MRM) using the precursor to product ion was m/ z 292.2/99.2 for fasudil, m/ z 308.2/99.2 for M3 and m/ z for 315.3/176.2 for IS. The linear range of the method was from 0.4 to 250 ng/mL for both fasudil and M3. The lower limit of quantification was 0.4 ng/mL for both fasudil and M3. The intra- and inter-day relative standard deviation over the entire concentration range was less than 7.11% for fasudil and 10.6% for M3, respectively. The validated method was successfully applied for the evaluation of pharmacokinetic of fasudil hydrochloride after administration of 30 mg fasudil hydrochloride by continuous intravenous infusion over 30 min in 12 healthy Chinese volunteers.