The effects of tree species(Picea crassifolia,Pinus tabulaeformis,and Platycladus orientalis)on gray-brown soil properties and water conservation in Qilian Mountains are studied.Results show that by total soil porosity,soil granular-structure,and soil clay content,tree species are in the order of Picea crassifolia Pinus tabulaeformi Platycladus orientalis;by soil density and soil sand content,in the order of Picea crassifolia Pinus tabulaeformis Platycladus orientalis;by soil organic matter and CEC,in the order of Picea crassifolia Pinus tabulaeformis Platycladus orientalis;by CaCO_3,pH,and total soil salt,in the order of Picea crassifolia Pinus tabulaeformis Platycladus orientalis;and by soil water storage and litter holding capacity,in the order of Picea crassifolia Pinus tabulaeformis Platycladus orientalis.