A high-performance liquid chromatographic method for the determination and pharmacokinetic study of mangiferin in the plasma of rats that have been orally administered the traditional Chinese medicinal preparation Zi-Shen pill is established. Plasma samples taken from rats are pretreated by protein precipitation with acetonitrile. Separation of the main effective constituent mangiferin is accomplished on a C18 stationary phase and a mobile phase of methanol&-water (25:75, v/v) with 0.6% glacial acetic acid. The UV detection wavelength is set at 320 nm, and the detection limit for mangiferin in plasma is 0.163 micro g/mL. After validation, the method is used to take a limited view of pharmacokinetic profiles of the traditional Chinese medicinal preparation Zi-Shen pill.