The Mu Us sandy land is located in the transitional zone from arid and semiarid to semihumid areas in China, and the study of species diversity and flora composition of natural plants have special significance. Based on the field investigation and statistics of natural plant species, the composition of the families, genera and species and flora composition of natural plants in the Mu Us sandy land are analyzed and compared with the adjacent sandy (desert) flora. (1) This area contains totally 772 species of natural plants, which belong to 90 families and 360 genera. The flora is relatively rich and the vegetation types are diverse, and the dominant families are obvious. The proportion of single species and few species account for 73.45%. (2) The natural flora of Mu Us sandy land is divided into 10 arealtypes and 4 variations in 90 families, and 360 genera are divided into 15 arealtypes and 10 variations.（3）The flora of Mu Us sandy land is dominated by Cosmopolitan, and the flora of the genus is mainly distributed in Temperate.There was a better pertinence between the characteristics of plants flora with the geographical location and climate. (4) The flora of Mu Us sandy land is very closed to Hunshandake sandy land, and less colosed to Kubuqi desert, Ulanbug desert and Kumtag desert. The results show that the flora of Mu Us sandy land is obviously distributed from Temperate to Mediterranean,West Asia and Central Asia.