Wind energy will affect the reliability of power system for its randomness and fluctuation. In this paper, the steady state model for the asynchronous generator is established and wind farms are considered as special PQ buses during power flow calculation. Combining with state models of conventional generating units, transmission lines and transformers, a time-sequential Monte Carlo simulation based on wind farm reliability model is established to do reliability assessment of composite generation and transmission system with wind farm. Meanwhile, an optimal load shedding model is used to decrease shedding load. IEEE-RTS test system is used to prove the proposed method. Analysis and comparison of results show that reliability can be improved clearly after integration of wind farm.