Abstract: In order to study the potential water conservation function of the soil of pine-oak mixed forest, the profiles were dug on the plots of three land use types in May of 2011, with the grassland and farmland as contrast. Then the soil physical properties, water-holding capacity and infiltration capacity were analyzed, and the potential water conservation capacity of soil was quantitatively evaluated by the method of comprehensive coordinate. Results showed that the order of soil bulk density from high to low was grassland (1.25 g/cm3)＞farmland (1.22 g/cm3)＞pine-oak mixed forest land (0.82 g/cm3). The rank of soil total porosity from high to low was pine-oak mixed forest land (87.40%)＞grassland (45.87%)＞farmland (38.95%). The pine-oak mixed forest land had the best water-holding capacity and infiltration capacity, and the farmland had the worst. The result using the method of comprehensive coordinate showed that the potential water conservation function of the soil of pine-oak mixed forest land was the best while the farmland was the worst, suggesting that the Reversion of Farmland to Forest Program should be kept on so as to raise the soil water conservation capacity in this region. This study provides basic data for cognizing and comprehensively evaluating the ecological service function of the pine-oak mixed forest in Huoditang forest region of Qinling Mountains, northwestern China, and offer theoretical basis for the water source protection of the Project of Diversion of Water from South to North.