Abstract: The Middle Route of South-to-North Water Diversion Project has been running for nearly 10 years.With the continuous construction of supporting facilities in the water-receiving area, the absorption capacity is gradually improved.When the water supply in the water source area is limited, the problem of competitive water use among the water-receiving areas is becoming increasingly prominent.In this paper, we proposed an allocation method of annual water supply for the Middle Route of South-to-North Water Diversion Project based on the design proportion of each province.The method was to firstly allocate the divertable water according to annual average distribution ratio of each province, which is considered as the initial allocation value, then take the smaller one between the initial allocation value and the water use plan of each province as its annual allocation water volume.We take the annual divertable water of 8 billion m3 of the Middle Route of South-to-North Water Diversion Project as an example to carry out the calculation.The results showed that according to the water use plan of the four provinces in the receiving area, by analyzing the water allocation situation, the water allocation of Beijing, Tianjin, Hebei and Henan was 1.04 billion, 0.856 billion, 2.8 billion, 3.0 billion m3 respectively.This method can provide a reference for the preparation of an annual water scheduling plan for the Middle Route of South-to-North Water Diversion Project and can provide support for ensuring the realization of the project's benefits.