Abstract: In order to solve the assignment problem of the wind/PV/battery hybrid power system, and to achieve the aim of independently providing clean, reliable and economic power for the area which is abundant in wind and solar resources, the paper presents an optimal design method of hybrid system based on the whole year's Loss of Power Supply Probability (LPSP) and the whole Life Cycle Cost (LCC). For the purpose of precise calculation of the system operation condition, a mathematic model of calculating method has been built for electric energy production of wind turbine, PV arrays and storage battery's behavior regime on the time interval of hour. By taking advantage of hybrid system, the optimal model to calculate the angle of PV arrays is also built. In addition, the model to calculate LPSP and LCC, which are taken as optimal index, is set up, and LPSP and LCC in all kinds of possible configurations are calculated based on iterative algorithm. The system configuration, which has minimum LCC and its reliability meet the requirement of LPSP, is obtained through reliability filtering of LPSP and economic optimization of LCC. This optimized design is calculated base on one-hour timescale, and result shows its high precision. LCC is taken as the economic index is feasible, and optimum angle of the PV arrays can play the key role of the system hybrid predomination.