To establish a ultra-high performance liquid chromatography-mass spectrum in series method for the quantification of 7-hydroxycoumarin，fraxetin，isofraxidin and scopoletin in the aqueous extract of Acanthopanacis Senticosi Radix et Rhizoma Seu Caulis in rat plasma，and to evaluate the pharmacokinetic behavior and bioavailability in rats.

The chromatography was performed on Thermo Scientific Hypersil GOLD aQ（100 mm×2.1 mm，1.9 μm）column with 0.1% aqueous formic acid -0.1% acetonitrile formic acid solution (82：18) as the mobile phase at the flow rate of 0.30 mL·min^-1，and column temperature of 40 ℃. Mass spectrometry positive ion mode scan was used，and sample size was 5 μL. Healthy SD rats were selected for a single gavage of 10 mL·kg^-1 of Acanthopanacis Senticosi Radix et Rhizoma Seu Caulis water extract (equivalent to the dose of 1 g·kg^-1 of the original drug). Plasma concentration of the substances was determined at different time intervals after administration，and the pharmacokinetic parameters were calculated using DAS software by non-atrioventricular model fitting.

The methodological results showed that 7-hydroxycoumarin (r=0.999 4)，fraxetin (r=0.998 9)，isofraxidin (r=0.999 3) and scopoletin (r=0.998 4) had good linearity in the range of 0.05-55 μg·mL^-1，and RSDs of precision of the four substances were all less than 15%. The recovery was 85%-115%. The absolute bioavailability ranged from 59% to 78%，and the relative bioavailability ranged from 80% to 87%. The extraction recovery，matrix effect and stability met the relevant requirements.

After a single gavage of the aqueous extract of Acanthopanacis Senticosi Radix et Rhizoma Seu Caulis in rats，the four substances to be tested are absorbed and eliminated by rats. The method validation results are in line with the guiding principles of biological sample analysis methods，and can be applied to evaluate the pharmacokinetic behavior and bioavailability of the aqueous extract of Acanthopanacis Senticosi Radix et Rhizoma Seu Caulis in rats.