Develop a HPLC-MS/MS method for the quantification of platycodin D (PD) in rat plasma and apply it to gain the main pharmacokinetic parameters of PD after oral administration of PD alone and Platycodi Radix extract. METHODS: Ginsenoside Rg1 was used as the internal standard (IS). After simple protein precipitation of the plasma samples with methanol, the analytes were separated on an ODS column (100mm×2.1mm I.d., 3.5μm) with the mobile phase of methanol-water (60:40, v/v) containing 0.1％ formic acid with a flow rate of 0.25mL/min. The detection was performed on a triple quadruple tandem mass spectrometry in the negative multiple reaction monitoring (MRM) mode via electrospray ionization (ESI) source with a chromatographic run time of 4.0min. RESULTS: The calibration curve was linear from 5 to 2000ng/Ml (r2＞0.99) with a lower limit of quantification (LLOQ) of 5ng/Ml. The intra- and inter-day precision (relative standard deviation, RSD) values were below 15％ and the accuracy (relative error, RE) was from -15％ to +15％ at three quality control (QC) levels. CONCLUSION: The method was successfully applied to assess the pharmacokinetics and oral bioavailability of PD in rats after administration of PD and Platycodi Radix extract.