In order to study the intestinal absorption behaviors of three active constituents, columbianetin acetate, osthole and columbianadin in Radix Angelicae Pubescentis extracts, in situ rat single pass intestine perfusion (SPIP) was carried out by the perfusion solution of the extract I containing less than 10% total coumarins. The absorption of extract II containing more than 60% total coumarins was compared with that of extract I by rat colon SPIP to elucidate the influence on absorption of the different coumarin content extracts of the Chinese traditional medicine. The samples of the perfusion solution were collected in certain intervals. The concentrations of three active components in the perfusion samples were determined by HPLC method. The results demonstrated that the absorption rate constants (Ka) or apparent permeability coefficients (Papp) of columbianetin acetate, osthole and columbianadin from extract I had no significant difference among concentration ranges of 62-555 microg x mL(-1), 101-887 microg x mL(-1), 19-186 microg x mL(-1), respectively. The absorption quantity of three components was proportional to its concentration respectively and the saturate absorption phenomena were not observed. This suggested that the absorption of columbianetin acetate, osthole and columbianadin showed the passive diffusion process. Three components could be absorbed in whole intestinal sections. The Ka and Papp of three components all showed colon > duodenum > jejunum > ileum in four different regions of rat intestine. At colon, Ka and P app were significant different from the others. The Ka or Papp of three components from the extract I was significantly more than that of same components from extract II. The extract I redounded to increase the absorption of three active components.