This paper researches the dispatching problem of a wind-solar-seawater pumped storage hybrid power system in sea islands, puts forward three kinds of dispatching methods of the hybrid power system, which include single dispatching, simple mixed dispatching and complex mixed dispatching. On basis of each kind of dispatching method, several kinds of related dispatching strategies are designed, including three kinds of single dispatching strategies, three kinds of simple mixed dispatching strategies and six kinds of complex mixed dispatching strategies. Taking Nanji Island for an example, first, this paper optimizes the capacity of the hybrid system of 12 dispatching strategies based on fuzzy multi-objective programming and genetic algorithm, then analyzes and compares operation results of optimal capacity allocation of 12 dispatching strategies, summarizes the advantages and disadvantages of the three dispatching methods and selects the best dispatching strategies. This work is supported by National High-tech R & D Program of China (863 Program) (No. 2014AA052003).