Radix Astragali (RA) is one of the commonly-used traditional Chinese medicines (TCMs) with an immunomodulatory effect confirmed in the clinic. In order to better understand the material basis for the therapeutic effects, this study was to investigate the absorbed components and their pharmacokinetic profile after oral administration of RA on cyclophosphamide-induced immunosuppression in Balb/c mice. As a result, 51 compounds in RA extract and 31 prototype compounds with nine metabolites were detected in mice plasma by the ultra-fast liquid chromatography (UFLC)-DAD-Q-TOF-MS/MS method. The pharmacokinetic parameters of five main constituents, including calycosin-7-O-glucoside, ononin, calycosin, formononetin and astragaloside IV, were obtained using HPLC-MS/MS. These results offered useful information for research on the pharmacological mechanism of RA and for its further development.