Abstract: The systematic evolution of Hedysarum (Leguminosae) distributed in Mongolian Plateau had been studied by Maximum Same Step Method of Xu Ke-xue. According to the results of cladistic study, the two new subgenera Subgenus Hedysara Y.Z. Zhao et al. and Subgenus Fruticosa Y.Z. Zhao et al. were erected in Hedysarum of Mongolian Plateau. Furthermore, the genus was subdivided into four sections, such as Sect. Fruticosa B. Fedtsch., Sect. Obscura B. Fedtsch., Sect. Multicaulia Boiss, Sect. Subacaulia Boiss, which was consistent with the treatment in "Flora of USSR"(1945).

Key words: Hedysarum, Cladistic taxonomy, Mongolian Plateau