Abstract: Ginsenosides is a key class of compound in Ginseng plant and was proved for many pharmacological efficacies such as anti-aging, memory enhancement and etc. Recent study indicates Ginsenoside Rh2 and Rg3 revealed antitumor activity. It is reported 39 Ginsenosides were separated and identified for the elemental composition and structure. An LC/MS approach to analyze new active compound is developed by using high resolution and tandem mass spectrometer which is considered to facilitate the discovery and identification of new chemical entity. In this work, the class compound of ginsenosides in Panax Ginseng extract were determined for accurate mass of both parent and product ions with multi stage fragmentation by using hybrid mass spectrometer LTQ-Orbitrap. Among total 37 compounds, 13 of them were confirmed based on accurate mass of parent ion, and other 24 were determined for mass at accuracy less then 1×10^－6. All compounds received single formula of elemental composition. An illustrated unknown ginsenoside was elucidated for structure unit aglycone and number of glycosyl.