Abstract: Based on the shortage of water resources in the north of China,under the condition of definite crops planting scale, the limited water resources were allocated to different crops in deficit irrigation ways,which aims to get maximum benefit.By means of simulative technique and the method of controlling the lowest water content rate of soil in different growth period, considering the randomicity of rainfall,the irrigation decision-making software was developed for the optimal water allocation and real-time self-adjustment in irrigation practice.