Abstract: To study how P-glycoprotein inhibitor verapamil affect pharmacokinetics of the active constituents Loureirin A, B and C in rat plasma after oral administration of Dragon's Blood,SD rats were randomly put into different group:control group and inhibitor group. A single dose of 5 g/kg of Dragon's Blood was orally administered to rats in control group, and rats in the inhibitor group were given verapamil (1 mg/kg) and Dragon' Blood (5 g/kg). Plasma samples were collected from the two groups in the same series of time. A HPLC-MS/MS method was used to determine the content of Loureirin A, B and C in rat plasma, and the plasma samples pharmacokinetic parameters were calculated. Comparing the area under curve (AUC0-t) of the rats in the inhibitor group with the control group, it increased by 109.4%,78.5%, 22.8%. And the peak concentration(C_max) of Loureirin A, B and C increased by 69.6%, 115.0%, and 42.1%. The time of Loureirin A and B reaching peak concentration (t_max) was prolonged, while the t_max of Loureirin C was unchanged. All three biological half-life (t_0.5) decreased. It indicates that P-glycoprotein inhibitor can significantly change the plasma pharmacokinetic parameters of Loureirin A, B and C in rats. Loureirin A, B and C may be potential substrates of P-glycoprotein. This article provides basic data for the subsequent in-depth study of the relationship between P-glycoprotein and transportation of Dragon's Blood in the intestinal tract of rats.