| As an important resource of agriculture, water resource exists serial problems in northwest China. In those places, the soil and water resources don't mach well and the distribution of water resource is not very suitable for agriculture. Especially In recently years, with the increasing of population and economic, the demand for water resources also increase. All of these enlarge the distance of demand and supply of water resources. It is important to study the agriculture water resources balance in northwest China. This paper systemically analysis the agriculture water resources balance in northwest China from two steps, and point out the calculation methods for both steps at the same time. At last, this paper takes Hexi corridor as the case study to analysis the water balance in northwest China. Results show that precipitation can not meet water demand of the crops is the main character in Hexi corridor. Deficit of water becomes increasing from west to east. When irrigation water is taken into account, there are some differences in those three river basins. Irrigation water can still not meet the crop water demand in Shiyang river basin, while it is a little well for Heihe basin, as for Shule basin, there still has some surplus water |