The changes of soil water of farmland(potato),woodland(acacia),cutting blank and grassland were simulated with SVAT-model(e.g.CoupModel) in loess hilly and gully region.In this paper,the degree of soil desiccation,contribute of climate drought and exhausting water by vegetation to soil desiccation and the hydro-ecological effects of soil desiccation were analyzed.The result showed there was soil desiccation in farmland and no soil desiccation in acacia woodland,cutting blank and grassland and especially soil desiccation were very serious in acacia woodland.The contribute ratio of climate drought and exhausting water by vegetation to soil desiccation were 70.74%,29.26% respectively,thus drought of climate is the main reason of soil desiccation.The soil desiccation can deal to the exchanged layer of soil water in profile shallow,mobility of soil water poor,and lose 77.58%~93.55% of regular capability of soil reservoir,form the isolation layer of water cycle,reinforce the dependency of vegetation to precipitation.In conclusion,the soil desiccation deteriorated the environment of hydrological cycle in the earth,affecting the natural growth of vegetation,making against ecological construction in loess hilly and gully region.