Abstract: We have conducted the research on the irrigation benefit, and set up the following experiments including slope runoff experiment, soil moisture content observation experiment, runoff-collecting experiment, water-saving irrigation experiment in the Xiji County of Ningxia. Then irrigation benefits were analysed with the observed data. The result indicates that the slope-separated terrace has the following benefits: retaining the runoff and sediment, preserving the moisture, increasing the soil moisture content, improving the soil nutrient and crop yield, etc., and the area ratio of the terrace to slope was put forward. It provides the essential theoretical foundation for the water-collecting irrigation of dry farm on Loess plateau.