An economic dispatching model of the power system considering wind power forecast error in the electricity market environment is developed. For a certain wind power forecast value， a Beta function is used to fit the probability density distribution of the real-time available output power. Considering the probability of the forecast error and the economic compensation cost they caused， a more reasonable dispatching model in statistics is proposed. The model is based on the more sound electricity market environment， and the cost of greenhouse gas emission right that needs to be considered by the power company is taken into account. A simulation case compares the effects of the wind power forecast errors on the market clearing price and average purchasing cost of the power grid. The result shows that the proposed model can effectively reduce the operating cost of the power company， and promote the optimal allocation of resources.