Abstract: The growth of Artemisia ordosica, which is the main community-constructing species,appears in some locations in the Maowusu sandland. Cynanchum komarovii, a perennial species; however, grows luxurantly throughout the area. There is obviously succession between these two species in experimental area. The characteristics of the two species are explained by our investigation based on physiological ecology, reproductive biology and by the analysis of fundamental elements of the environment.A. ordosica and C. komarovii are characteristic of anisohydric and isohydric plants respectively. The photosynthesis, transpiration and stomatal behavior of the two species are distinctly different from one location to another. The water-use efficiency of C. komarovii is much higher than that of A. ordosica. Furthermore, C. komarovii is more drought resistant and therefore less sensitive to water stress; A. ordosica, however, is less tolerant therefore more sensitive to water stress. The result is that C. komarovii is more dominant than A. ordosica in survival competetion.In conclusion, one of the main external factors of succession is the water content of the soil; the major internal factors of succession are the distinctive water physiological-ecological and reproductive biological characteristics of the two species.