In order to explore the dominating influences on the composition of vegetational community in the Qaidam Baihe River Basin of Chengde, Hebei Province, for supporting the ecological environment protection, the authors conducted detailed investigation of the community and field survey of the geological formation as well as test on elemental geochemistry, and then analyzed the response of vegetational community composition to the geological formation, which includes granite intrusive rock, rhyolite volcanic rock, dolomite carbonate rock and sandy conglomerate clastic rock from the perspective of spatial feature, nutrient as well as water supply under the similar climate condition. The granite formations are characterized by thick soil, non-continuous fractures, high nutrient content of phosphorus and optimal water retention capacity, which are favorable for the deep-rooted arborous species. The rhyolite formations have relatively less thickness of soil, with interpenetrating fractures in the substrate, high nutrient content of phosphorus, but relatively poor water retention capacity compared with granite formations, which are beneficial to deep-rooted shrub. The dolomite formations have the features of thin soil layer, with tightly closed through fissures, high nutrient content of calcium, but poor water retention capacity, which are favorable for the growth and development of shallow-rooted shrub and a small amount of calcium-like shallow-root trees. Compared with another formations, the dolomite formations are characterized by the thinnest soil, low nutrient content, and poor water retention capacity, without fracture developing, which are suitable for the drought-tolerant shrub.