In this paper, a probabilistic production simulation (PPS) based on the equivalent energy and frequency function method is proposed to analyze the power supply reliability and the production cost of a wind-photovoltaic (PV) hybrid generation system. Compared with the wind power generation system that has the same installed capacity, the wind-PV hybrid generation system increases the value loss of load probability (LOLP) and expected energy not supplied (EENS), but reduces the volatility of the output and frequency of generator start-stop of unit capacity (FGSUC) due to the complementary nature between wind and solar energy. So the production cost can be reduced. Simultaneously, the optimization method of the windsolar hybrid generation system capacity is proposed, which target is to achieve a minimum production cost. The case studies has been carried out on an EPRI 36-bus system, and the results demonstrate the effectiveness of the proposed method.