Central part of Onon-Dahuria region covers plain territory of the Onon river basin in limits of Onon plain and Zugol steppe. On the base of original data and early published information, the check-list of the vascular flora is compiled. The list includes 802 species and subspecies from 358 genera and 91 families. For every species, frequency as well as typical habitats within the investigated area are outlined. Rare species are supplemented by quotation of concrete localities. 96 species are registered in the region of Onon Dahuria for the first time.