This work aims to elucidate the chemical constituents of Kai-Xin-San(KXS) and its metabolites in rat plasma.KXS extracts were separated on an Agilent HPLC SB-C 18 column,analyzed by ion-trap tandem mass spectrometry and high-accuracy qTOF mass spectrometry in negative ion mode.A total of 39 compounds,including 11 ginsenosides,14 Polygala saponins,5 sucrose esters,8 oligosaccharide esters and 1 xanthone were characterized from KXS.Fifteen of them were confirmed by reference standards.No constituents were detected from Poria or Acori Tatarinowii Rhizoma.After oral administration of KXS(7 g/kg),10 ginsenosides and 18 Polygala compounds were detected in rat plasma.This study indicates that ginseng saponins,Polygala saponins and saccharide esters could be the major effective components of KXS prescription.