Abstract: This paper is analysed the ecological relationship between the spatial structure of each vegetation level (large, medium, small, fine) of the Xilin Gol Steppe in Inner Mongolia and the corresponding environmental factor by analysing their remote sensing images. The ground biomass and the theoretical livestock-carrying capacities of each vegetation type are estimated. The results show that the separation tendency of vegetation of Xilin Gol Steppe is clear, the large structure of vegetation is determined by large climatic factors, and large geomorphologic unit, and the landform and hydrological network are the primary factors affecing the medium structure of vegetation, but the small and micro structures are controlled mainly by local landform,surface water, matrix and human activities.