A combination of Angelicae Dahuricae Radix and Acori Tatarinowii Rhizoma has been widely used as the herb-pair in traditional Chinese medicine to treat stroke, migraine and epilepsy. However, the underlying synergistic mechanism of the herb-pair remains unknown. This study was aimed at investigating the effects of Acori Tatarinowii Rhizoma volatile oil on the pharmacokinetic parameters of xanthotoxol, oxypeucedanin hydrate and byakangelicin from Angelicae Dahuricae Radix in rat, and in vitro absorption behavior of the three compounds using rat everted gut sac, in situ single-pass intestinal perfusion and Caco-2 cell monolayer models. The pharmacokinetic study exhibited clear changes in the key pharmacokinetic parameters of the three main coumarins through co-administering with Acori Tatarinowii Rhizoma volatile oil (50 mg/kg), the area under curve and the maximum plasma concentration of xanthotoxol increased 1.36 and 1.31 times; the area under curve, the maximum plasma concentration, mean residence time, half-life of elimination and the time to reach peak concentration of oxypeucedanin hydrate raised 1.35, 1.18, 1.24, 1.19 and 1.49 times, respectively; the area under curve, mean residence time, half-life of elimination and time to reach peak concentration of byakangelicin climbed 1.29, 1.27, 1.37 and 1.28 times, respectively. The three coumarin components were absorbed well in the jejunum and ileum in the intestinal perfusion model, when co-administered with Acori Tatarinowii Rhizoma volatile oil (100 μg/mL). The in vivo and in vitro experiments showed good relevance and consistency. The results demonstrated that the three coumarin compounds from Angelicae Dahuricae Radix were absorbed through the active transportation, and Acori Tatarinowii Rhizoma volatile oil could promote the intestinal absorption and transport of these compounds via inhibiting P-gp-mediated efflux. This article is protected by copyright. All rights reserved.This article is protected by copyright. All rights reserved.