Abstract: In order to discuss the relationship of dynamic response between community of Caragana korshinskii，environmental factors and soil moisture，the sampling sites were selected on mature forest of Caragana korshinskii under different terrain conditions at scale of watershed in semiarid loess area. Soil moisture in the 0-220 cm soil layers was measured biweekly in each sampling site from the beginning of May to the end of October during 2009-2011，and the soil moisture in the 0-600 cm soil layers was measured in August of 2010. The investigation on community structure characteristics of Caragana korshinskii was conducted in September 2011. The multiple comparison and the analyzing-plotting were carried out using SPSS 17.0’s Duncan and Excel 2007，the soil moisture differences in different soil layers，variance on season of growth in different years，the degree of desiccation and environmental impact factors have been done a comprehensive analysis. The results showed that：for the shallow layers，the results are as follows：soil moisture content of north slope＞one of east slope＞one of south slope，and one of below slope position＞one of upper slope position，and there is a negative relationship between the slope gradient and soil water content. The sequences of PCSWDI are as follows：for 0-220 cm layers，upper slope position of south slope＞middle slope position of south slope＞upper slope position of north slope＞lower slope position of south slope＞lower slope position of east slope＞upper slope position of south slope＞lower slope position of north slope＞middle slope position of east slope；for 220-600 cm layers，middle slope position of east slope＞lower slope position of south slope＞lower slope position of north slope＞middle slope position of north slope＞upper slope position of north slope＞lower slope position of north slope＞upper slope position of east slope＞middle slope position of south slope＞upper slope position of south slope. From the surface layers to deep layers，the influence of vegetation to the soil moisture content is stronger than that of terrain condition. In a certain community of Caragana korshinskii，a clear negative relationship exists between vegetation growth conditions（coverage and height）and deep soil moisture content. Artificial vegetation increases the degree of soil desiccation，and the continuous drought can lead to temporary dried soil layer. However，a permanent dried soil layer forms gradually from primarily development to mature stage in the succession process and exists all the time. The research on the correlation between soil moisture and community spatial structure of Caragana korshinskii has a certain innovation.

Key words: semiarid loess area, mature forest land of Caragana korshinskii, soil moisture, heterogeneity, impact factor, desiccation