Tripterine is one of the main active components in tripterygium wilfordii polyglycosides tablets. Cyclosporine A (CsA) is an immunosuppressive agent commonly used in clinical organ transplantation. Combined application of Tripterygium wilfordii and cyclosporine A has been proved to enhance the immunosuppressive effect of cyclosporine and reduce its toxic effects. The present study investigated the effect of tripterine on the pharmacokinetics of CsA and its underlying mechanisms.LC-MS/MS was used to establish a detection method of the concentration of CsA in rat blood. Polymerase Chain Reaction (PCR) and Western Blot (WB) were used to determine the expression of tripterine on drug metabolizing enzymes (DMEs), drug transporters (DTs) and nuclear receptors (NRs). As the result, tripterine reduced the bioavailability of cyclosporin A. Compared with control group, the Cmax of CsA were reduced in all dosages of tripterine, and the AUC was significantly decreased in 18 mg∙kg-1 and 54mg∙kg-1 group. The results of PCR and WB showed that tripterine had inhibitory effects on CYP3A1, CYP3A2, UGT1A1, OATP1B2, P-GP, MRP2, BCRP, BSEP and NTCP. Therefore, we put forward that the inhibition effect of tripterine on NTCP, BESP and OATP1B2 in the liver could limit the uptake of cyclosporin A into the blood and the hepatointestinal circulation of cyclosporine A, resulting in the decrease of blood drug concentration of cyclosporin A.