The roots of Angelica dahurica cv. Qibaizhi is frequently used in clinical practice as a traditional Chinese medicine. However, a comprehensive study of the pharmacokinetics of this medicine has not been carried out. A sensitive and specific liquid chromatographic-tandem mass (LC-MS/MS) spectrometric method was established to investigate pharmacokinetics of sixteen coumarins of Angelicae dahuricae Radix (ADR) in rat plasma, including xanthotoxol (1), oxypeucedanin hydrate (2), 5-hydroxy-8-methoxypsoralen (3), (-)-marmesin (4), byakangelicin (5), columbianetin (6), psoralen (7), xanthotoxin (8), neobyakangelicol (9), isoimpinellin (10), bergapten (11), heraclenin (12), oxypeucedanin ethanolate (13), imperatorin (14), phellopterin (15), isoimperatorin (16). Detection was performed on a triple quadrupole mass spectrometer in multiple-reaction-mode (MRM). The method established in this assay was successfully applied to the pharmacokinetic study of the selected coumarins in rat plasma after oral administration of the extract of ADR, and the pharmacokinetic characteristics of sixteen coumarins were clearly elucidated. This pharmacokinetic identification of multiple coumarins of ADR in rats provides a significant basis for better understanding the metabolic mechanism of the herb medicine.