Abstract: The responses of phenophase and morphological traits of four kinds of annual species in steppe and desert regions in Inner Mongolia to rainfall variation were analyzed by an experiment in which four precipitation gradients (5, 20,70 and 150 mm) were used to simulate effective rainfall in steppe and desert regions. The growing season of annual plant groups in these regions is usually 40 to 90 (<100) days. The growing season, plant height, leaf length, and biomass of annual plants increased with an increase of rainfall. The life history of annual plants can basically be completed with 5 mm effective rainfall, but their growth and propagation are best in 70 mm effective rainfall. The change of phenophase in Salsola collina was smaller than that of other annual short grasses, and was done by adjusting the length of the reproductive stage and reducing fruit bearing as a response to lack of rainfall. Annual short grass can adjust the length of every phenophase to adapt its growth and reproduction to rainfall variation. In the same conditions of rainfall, the growing time of annual short grass is relatively longer than that of S. collina but the latter showed stronger drought-avoidance ability, while annual short grass has stronger drought-resistance ability in its adaption strategies.