To study the absorption mechanism of tanshinones in the roots of Salvia miltiorrhiza as well as the interaction between the components in the effective fraction.The model of intestinal absorption in vivo was used and the concentrations of the tanshinones were determined by HPLC, the apparent absorption constant (K(a)) and half life of absorption (t1/2) were obtained, the other components in the extract on the absorption of the there components were also studied.With the increase of dosage of tanshinone II A or cryptotanshinone, K(a) decreased and absorption half life t1/2 increased, the drug absorption rate constant (K(a)) had little significant effect on duodenum, Jejunum and ileum. Tanshinone I has a good absorbing in the rat small intestine. The absorption of tanshinone II A and cryptotanshinone was promoted by the other components in tanshinones extract while tanshinone I' was decreased.When the concentration increases to a certain level, the uptake of tanshinone II A and cryptotanshinone do not increase. The transport mechanism of tanshinone II A and cryptotanshinone in vivo is similar to active transport or facilitated diffusion. They could be well absorbed in general intestinal tract without specific absorption site, and the complex constituents in extract could significant effect the absorption of the pharmaceutical effective constituents.