Tanshinone IIA (TSNIIA) is the major active component of Salvia miltorrhiza, which is used in treatment of cardiovascular and cerebrovascular diseases traditionally in China. However, the low bioavailability of TSNIIA limits its clinical usage. To reveal the mechanism relating the absorption of TSNIIA, we detected the expression of efflux transporters in Caco-2 cells under the stimulation of TSNIIA. TSNIIA was purified and above 98% purity was confirmed by high-performance liquid chromatography. The expression of nine efflux transporters including BCRP, hPepT1, MCT and MRP1-6 in Caco-2 were verified by reverse transcription polymerase chain reaction, and the up-regulation of TSNIIA on the expression of these transporters was found by reverse transcription real-time polymerase chain reaction. These results indicate that the low bioavailability of TSNIIA is partially due to its up-regulation on efflux transporters.