Solar-air source heat pump hot water system (SAHWS) is commonly used in dormitory building heating, through the optimization of system parameters can significantly improve the energy efficiency and environmental friendliness of the system. In order to obtain an optimization method that comprehensively considers the SAHWS economy, energy, environmental protection and energy saving, this paper proposed a new combination optimization design strategy, and used TRNSYS software to build a system simulation model. Taking Xi'an, Xining and Lhasa, which are three cities with different levels of solar energy resources, as examples. Comparative analysis of SAHWS operating conditions. The results show that compared with the common life cycle cost design, the proposed combinatorial optimization design not only reduces the system cost, but also reduces the system energy consumption. The heat pump designed by combination optimization has the shortest energy consumption and working hours, and has the lowest heat loss. It has better performance in investment cost, system seasonal performance factor, solar energy guarantee rate, carbon dust and carbon dioxide emissions.