Abstract: Forest soil is the regulator and reservoir of water and nutrients, and also the comprehensive embodiment of the structure and function of forest stand in the small water cycle of forest ecosystem. In this paper, five typical vegetation types of forest soil in the alpine area of Qilian mountains were taken as the research object. Soil bulk density, porosity and soil permeability were measured and the characteristics of understory soil were studied. The results showed that the average soil bulk density of typical values was in the order from small to large: Qinghai spruce forest < wet irrigated forest < Qilian cylindrica <dry irrigated forest < pasture slope grassland < no forest. The order of non-capillary porosity from large to small was: Qinghai Spruce forest > wet irrigated forest > Qilian huanbolin > dry irrigated forest > grazing slope grassland > no forest. The indexes of soil static water storage capacity of Qinghai spruce forest were better than other vegetation types, followed by wet irrigated forest and no forest, and the indexes of wet irrigated forest were second only to Qinghai spruce forest. The soil surface permeability of Qinghai spruce forest is several hundred times higher than that of other soil surface, and the seepage velocity is more than 1000times higher. The soil surface stability permeability of grassland is only 0.43% of that of Qinghai spruce forest, and the bottom soil layer is only 30%.