Abstract: In order to achieve fuel economy optimum of hybrid power system designed with dual-planetary architecture, factors of energy saving effects were investigated for configuration scheme of parallel-series hybrid power system. The results showed that by energy storage mechanism and matching character for the objective of improving system fuel economy the operation status of vehicle were determined, and then design method optimized for energy storage element based on usual working conditions was proposed with fuel economy as a target, the optimization algorithm model was set up to optimize the parameters of energy storage system. The methods were verified by some classic duty cycle and combined with mathematic modeling and simulation, and it was concluded that the fuel economy of hybrid power system was improved by 4%. This research provides a reference for further optimization of more parameters and application of advanced control algorithm.