The paper is to report the development of a high-performance liquid chromatographic/tandem mass spectrometry (HPLC-MS/MS) method for the determination of icaritin (ICT) in rat plasma.  After     precipitated with acetonitrile from the plasma, ICT was isolated chromatographically on a Dikma C₁₈ column.  The mobile phase consisted of acetonitrile-water-acetic acid (72∶28∶1.5, v/v/v).  Electrospray ionization (ESI) source was applied and operated in the positive ion mode.  Multiple reaction monitoring (MRM) mode with the transitions of m/z 387 → m/z 313 and m/z 331 → m/z 315 were used to quantify ICT and the internal standard, respectively.  The linear calibration curve was obtained in the concentration range of 2.5−1 000 ng·mL⁻¹.  The lower limit of quantification was 2.5 ng·mL⁻¹.  The inter- and intra-day precision (RSD) were less than   9.63%, and the accuracy (relative error) was within ±7.42%.  The method was proved to be suitable for the pharmacokinetics of ICT, which offers advantages of high sensitivity and selectivity.