[Objective] Research on the dynamic characteristics of soil moisture under different vegetations in different seasons in loess hilly area of Northwest Shanxi Province in order to provide conferences for the selection of appropriate species of vegetation in this area in vegetation construction process.[Methods] This study takes the different types of vegetation and abandoned land in the Loess Hilly Area of Kelan County, Northwest Shanxi Province as the research subject. The author chose the three representative vegetation types in this area as the main object, which including Populus simonii as the representative of arbor, sea buckthorn as the representative of shrub, and abandoned land. The vertical dynamic variation of the soil moisture in the dry season(April) and rainy season(September) of these vegetation types from different surface was systematically analyzed.[Results] The soil moisture of the three vegetation types in September was significantly greater than in April, showing the overall trend was increased, then reduced and increased again from the depth of the surface to 600 cm. The order of soil moisture content of each woodland is:abandoned land> sea buckthorn> populus simonii. Soil dry layer standard of loess hilly region:mild dry layer, moderate dry layer and serious dry layer.[Conclusion] In the process of vegetation restoration and reconstruction in Northwest Shanxi Province, it is essential to adjust the structure of land utilization, improve the proportion of arbors, shrubs and grass, diversify the vegetation, establish a sustainable mixed and re-storied forests and a relatively balanced plant communities with rational population density, and to ensure the water supply by the environment and water consumption of the vegetation is in a stable state.