The peak-valley load difference of urban power grid leads to a large waste of power resources. Urban power network couped to hydrogen energy storage system is proposed here to dissipate surplus power during low load period. Based on the analysis of investment cost and economic benefit in the life cycle of hydrogen storage system, an evaluation model for investment decision making is built which involves three optimization models according to the different investment demands: the minimum hydrogen selling price model, the optimal installed capacity model and minimum selling price model under given payback period. Finally, based on the real data of a certain city grid load, the optimal scheme is analyzed under the different investment demand when the urban power grid coupled to hydrogen energy storage system is implemented in the city.