OBJECTIVE： To establish a method for the content determination of sinapine thiocyanate， quercetin and kaempferol in rat plasma， and to study pharmacokinetics of Qili qiangxin capsule in rats in vivo. METHODS： HPLC-MS/MS method was adopted. The determination was performed on ZOBRAX XDB-C18 column with mobile phase consisted of 0.1％ formic acid solution and acetonitrile containing 0.1％ formic acid （gradient elution） at the flow rate of 0.45 mL/min. The sample size was 10 μL. Quantitative ions were sinapine thiocyanate with m/z 310.2→251.2， quercetin with m/z 301.1→150.7， kaempferol with m/z 286.2→242.0， internal standard chloramphenicol with m/z 320.9→ 151.9. 0.083， 0.167， 0.333， 0.667， 1， 1.5， 2， 3， 4， 6， 8， 12， 24 h after intragastric administration of Qili qiangxin capsule 1.3 g/kg， blood samples were collected via intraocular canthal venous plexus of 6 rats. The blood concentrations of sinapine thiocyanate， quercetin and kaempferol were determined. The pharmacokinetic parameters were calculated and fitted by using DAS 3.0 software. RESULTS： The linear range of sinapine thiocyanate， quercetin and kaempferol 0.05-100， 0.1-200， 0.1-200 ng/mL（r＝0.999 4， 0.999 7， 0.999 9）； RSDs of precision test and matrix effect were all less than or equal to 11.55％ （n＝6）， RE of stability test is less than or equal to 14.69％ （n＝3）. The pharmacokinetic parameter of sinapine thiocyanate， quercetin and kaempferol included that cmax were（1.35±0.62），（3.23±1.26），（5.27±1.66）      ng/mL； tmax were （1.50±0.00）， （0.67±0.00）， （0.67±0.00） h； t1/2 were （3.98±0.99），（3.33±0.41），（4.54±0.85） h； CL were （3 683.82±987.96）， （2 852.33±695.88），（1 611.85±129.59） mL/（h·kg）； AUC0-24 h were （3.98±1.21）， （10.96±3.42）， （13.59±5.35） h·ng/mL. CONCLUSIONS： Established method is highly sensitive， specific and reproducible， and suitable for the pharmacokinetic study of sinapine thiocyanate， quercetin and kaempferol in rat.