Water use efficiency of C4 plants is higher than that of C3 plants, and CAM(Crassulaceae acid metabolism) plants have the highest water use efficiency. In the desert regions of China, CAM plants are scarce, and C4 plants, especially C4 woody plants, have an important position and role in the desert ecosystem. There are 45 species of C4 woody plants in the desert regions of China, including semi-woody plants, which account for 6% of total desert plant species in China, and most of them concentrate in the families of Chenopodiaceae and Polygonaceae, which are 19 species and 26 species, respectively. The numbers of C4 herbaceous plants are 107 species, including 48 species of monocotyledon and 59 species of dicotyledons. C4 woody plants mainly inhabit in the northwestern arid desert region of China to the west of the Helan Mountains. The drought-resistance and drought-tolerance in C4 herbaceous plants are worse than C4 woody plants, and the C4 herbaceous plants mainly inhabit in the areas with shallow groundwater and better water conditions in desert regions, and widely distribute in the edge of oasis. The abundance of C4 woody plants is closely correlated with drought, but the abundance of C4 herbaceous plants increases with wet conditions.