Abstract: To analyze and identify the constituents in rat plasma after oral administration of the active fraction of cistanche, the components in rat plasma were detected by high performance liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry (HPLC-Q-TOF MS). Structures of the components were elucidated by comparing their retention times and MS/MS spectra with those of reference compounds and reported data in the literatures. 13 chemical compositions are identified, including 6 prototype components, such as Geniposidic acid, Salidroside, Cistanoside A, Echinacoside, Acteoside, Cistanoside D, 7 metabolites components, such as 3,4-Dihydroxyphenylethanol glycosides, methylation acteoside, acetylation Cistanoside G, 3,4-Dihydroxyphenylethanol, acetyl tubuloside B, Cistanoside B glucuronide metabolite and methylation-3,4 Dihydroxyphenylethanol. The results can provide essential data for illuminate the therapeutic basis of quasi estrogen regulation activity of cistanche.