A typical case of water allocation was summarized to provide the foundation for distributing water. The water allocation plan of the Luanhe-Tianjin Water Diversion Project was discussed in this paper. The index system was set up for assessing the water allocation. The system includes four layers， 4 indexes in the criterion layer， 10 indexes in the connotation layer， 20 indexes in the indicator layer. The organization and implementation of the water allocation in the recent 30 years was comprehensively evaluated using ELECTRE Ⅲ. The result shows that the water allocation plan is scientific， implementation process of the plan is reasonable， supervision mechanism and management system of the implementation process are complete， and the plan implementation effect is remarkable.