Objective: To develop a LC-MS-MS method to determine pteryxin concentration and its metabolite in rats plasma. Method: Blood samples were collected at different time after oral administration of Peucedunum harry-smithii var subglabrum extract at doses of 80 mg ·kg-1. The pteryxin concentration and its metabolite in plasma was determined by LC-MS-MS. Pharmacokinetic parameters were fitted by DAS 2.0 software package. Result: The linear range and the average recovery of pteryxin were 0.132 5-53.00 μg ·L-1(r =0.999 2)

and more than 83% (n=5)

respectively. The inner and inter-days precision were both less than 10%. Conclusion: The method described in this report has high sensitivity and selectivity

and was suitable for pharmacokinetic study of pteryxin.The process of pteryin in palsma showed two compartment model after oral administration of Peucedunum harry-smithii var subglabrum extract at doses of 80 mg ·kg-1 to rats.