Based on literature review and field investigation, the seed plants flora of Xilin Gol Grassland National Nature Reserve were investigated and analyzed. Meanwhile, the species composition, water ecotypes and geography elements of seed plants in this area were counted by statistic method. The results showed that there are 856 species wild seed plants which belong to 345 genera and 87 families. Of which, there are 11 Gymnosperms species which belong to 5 genera and 3 families; 845 Angiosperm species which belong to 340 genera and 84 families. There are 559 species of mesophytes, accounting for 65.30% of the total species of the flora; and 213 species of xerophytes, accounting for 24.88% of the total species of the flora. The lifestyle is mainly herbaceous plants, accounting for 88.67% of the total species of the flora. The types of floristic geographical elements are complex, which reflects not only the strong regional characteristics of plants in the reserve, but also the characteristics of diverse habitat types and high plant richness in the region.