It is crucial to further understanding the mechanism of ecosystem process and functions,and proposing the ways to cope with the effects of climate change through revealing the dynamic change of soil moisture content in arid and semiarid ecosystems. In this study, the dynamic change of soil moisture content and its response to rainfall were explored using the precipitation data in recent 50 years from a nearby meteorological station based on the data of soil moisture content (15 cm in depth) and of precipitation in recent continuous 4 years in a steppe. The results are as follows: ① Affected by precipitation distribution pattern, the curves of dynamic change of soil moisture content in the steppe were unimodal and bimodal; ② There was no response of soil moisture content to rainfall less than 5 mm. However, the soil moisture content could be significantly increased when rainfall was more than 18 mm. Moreover, rainfall needed by soil was higher than that by sandy land and desert; ③ Response of soil moisture content to rainfall was rapid when rainfall and its intensity was high or soil moisture content was high before rainfall. Climate change in the future will possibly be disadvantageous for the growth of shallow rooting plants, thus it will impact seriously the animal husbandry.