According to field investigation,specimens identification and literature survey,we studied and discussed the diversity and floristic characteristics of seed plants in the Inner Mongolia Baiyinaobao National Nature Reserve.Meanwhile,the comparison of flora similarity between Baiyinaobao and other four locations around (Zhangtutai,Mulan Poddack,Dalinuoer and Wusitu) was analyzed.The results showed that:(1)There are 526 species of wild seed plants which belonging to 261 genera and 72 families in the Baiyinaobao Nature Reserve.The species richness was relatively high,but vulnerable.(2)For the family composition of the flora,there are eight dominant families,and for genus composition,there are 246 monotypic and small-sized genera which accounting for 94.26% of the total genera.For the life forms,herbs were predominant and for the water ecotypes,the mesophytes were most abundant.(3)For the areal-types,the temperate elements were dominant and the flora was remarkably characterized by temperate zone in nature.On the other hand,the origin of some elements of the flora was ancient,but the endemic was low.(4)Compared with other four floras around,Baiyinaobao has the highest genera similarity with Dalinuoer,and has relative low similarity with Wusitu.