Abstract: AimTo develop a sensitive and rapid HPLC method for the determination of tanshinone IIA (TS) in rat plasma and to study its pharmacokinetics in rats. MethodsTS and 4-chlorodiphenyl (internal standard) were extracted from plasma with ethyl acetate. After liquid-liquid extraction, the sample was analyzed by HPLC with YMC C¹⁸ column (5 μm, 150 mm×3.0 mm ID). The mobile phase consisted of acetontrile-water-acetic acid (74∶26∶1) at the flow rate of 0.3 mL·min^-1, the UV detection wave length was 270 nm. ResultsThe calibration curve was linear (R=0.998 1) in the range from 0.05 to 6.40 mg·L^-1. The lowest detectable concentration was 0.05 mg·L^-1. The recoveries at the concentration of 0.05, 1.60 and 6.40 mg·L^-1 were 98.9%, 102.1% and 100.4%, respectively. The inter- and intra-day RSDs were all less than 5%. ConclusionThis method is proved to be rapid, precise and reliable enough to be applied to the pharmacokinetics studies of TS in rats after a single dose of 15 mg·kg^-1 by oral administration.