In order to solve water use conflict occurred in different water requirement departments at the irrigation districts in the west of Guanzhong Region under emergent drought situation, the authors set up a regional optimal water allocation model which aimed at largest total water use quantity at the four irrigation districts by using dynamic programming based on hierarchical theory of large system. Three types of first class choice schemes (the third one is made up of 27 second class choice) for water distribution were made according to different frequencies combination between water needs and inflow. Based on the analysis results of various options scheduling, and considering the actual operation interoperability, water transfer quantity in summer irrigation was taken as main control factor. Through classification and combination, the third scheme was recommended, which includes 11 types of water transfer schemes for four irrigation districts. Satisfied results were obtained by applying the scheme during 2005―2007. This scheme provides scientific basis for emergency water transfer on drought combating.