Morroniside, an iridoid glycoside extracted from Cornus officinalis, has multiple pharmacological effects such as neuroprotection. This study took the lead in establishing a method for determining morroniside concentration in rat plasma by high performance liquid chromatography-tandem mass spectrometry. Plasma samples were processed with protein precipitation method, with hyperoside as the internal standard. An Inertsil C8-3 column (2. 1 mm x 50 mm, 5 microm) was adopted, with a mobile phase composed of water (containing 1 mmol L-1 Sodium formate)-acetonitrile (gradient elution) at a flow rate of 0.4 mL . min -1. Electrospray ionization (ESI) was adopted in the positive ion mode for multi-reaction monitoring (MRM). Morroniside showed a good linear relationship ranging between 2-5 000 microg L-1 (r = 0. 995 7), with the minimum limit of quantification of 2 microg L-1. Its precise, accuracy, recovery and matrix effect were all in line with the biological sample measurement requirements. Therefore, the method described above was proved to be suitable for the determination of morroniside concentration in rat plasma. To use the method in the pharmacokinetic study on morroniside in rats, oral administration dose shall be set at 20 mg . kg - to map the plasma concentration-time curve. Main pharmacokinetic parameters were calculated by DAS 2. 0. Specifically, AUC0-inifinity was (587.6 +/- 290. 7) microg min L-1, Cmax was (334.2+/-148.0) microg L-1, Tmax was (0.6 +/-0.3) h, t1/2 was (0.7+/-0.3) h.