A simple, sensitive and selective high-performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) method was developed and validated for simultaneous determination and pharmacokinetic study of 15 active compounds (Saikosaponin A, Baicalin, Wogonin, Glycyrrhizic acid, Glycyrrhetinic acid, Albiflorin, Paeoniflorin, Liquiritin, Isoliquiritin, Liquiritigenin, Isoliquiritigenin, Cinnamic acid, Gallic acid, Wogonoside and Oroxylin A) in rat plasma. After a feasible protein precipitation using methanol for sample preparation, chromatographic separation was carried out with a Halo® C column (2.1 × 100 mm, 2.7 μm) at 35 °C, water containing 0.1% formic acid and acetonitrile were used as the mobile phase with a flow rate of 0.3 mL/min. Multiple reaction monitoring (MRM) with positive and negative ion switching mode was performed for the quantification of the standards and internal standard in plasma. All the calibration curves showed good linear regression within the linear range (r > 0.9923). In particular, the results of the method validation including specificity, linearity, accuracy, precision, extraction recovery, matrix effect, and stability of compounds in bio-samples were all within the current acceptance criteria. The established method was successfully applied to the pharmacokinetic study of 15 compounds in rats after oral administration of CGD and laid the foundation for studying the active components and mechanism of CGD in vivo.