Abstract: How to improve the utilization rate of water and increase the efficiency of power generation has always been the main goal and direction of hydropower dispatching research. Based on the traditional optimal dispatching, an optimal dispatching model of cascade hydropower station based on the maximization of unstored power is established in this paper, which takes the utilization of the unstored water of the reservoir as the starting point. Through an analysis of the dispatching model and the application of POA algorithm to solve it, and combined with the verification of an engineering example, the rationality and feasibility of the model and method are illustrated. Compared with the traditional dispatching mode, the dispatching model provided in this paper can improve the power generation utilization rate of unstored water by reasonably adjusting the output distribution of each cascade power station according to the change of power network load demand under various constraint conditions. It indirectly reflects the saving and utilization of water resources and is helpful to the arrangement of joint dispatching mode of cascade hydropower stations, and can promote the development of optimal dispatching of cascade hydropower stations to a certain extent.