Changes in the forest-steppe ecosystem plant biomass during the 2008-2014 study of the Khentii mountain areas, at the Terelj river basin was conducted. Tundra, forest, meadow vegetation types distributed in this basin. About 30 percent of forest vegetation in the basin, more than 20% of steppe and dry steppe vegetation. Terelj River Basin included high mountain district of the Khentii, of the Inner Baigal region, coniferous forest-meadow steppe region of Eurasia zone in Mongolian plant and geographical classification.