Abstract: Based on the comprehensive view of resources,economy,society,environment and other influencing factors on the optimal allocation of water resources,and following the principles of water right allocation,the index system of water quantity and the hierarchical chart of water right allocation are developed.Methods of fuzzy synthetic decision-making and analytical hierarchy process are used to do the optimal fuzzy selection on a multi-project and multi-hierarchy basis,then the mathematical model of initial water right allocation is set up.And the water quantity allocation of the eastern rout of South-to-North Water Diversion Project in the first period is carried out.