The existing wind power forecasting methods can not reduce the error to a negligible range. The integration of wind power will increase the uncertainty of power system, which may lead to difficulty of power system dispatching. And, as an important measure of electric power market reform, the introduction of large consumers direct purchasing has brought new challenges to power system dispatching. Therefore, a power system economic dispatching model considering the uncertainty of wind power and large consumers direct purchasing is established in this paper. The model aims to maximize the profit of power generation system based on the safe operation of power system. Beta probability function is presented to consider the increase of the upper and lower spinning reserve demand caused by the uncertainty of the wind power. Similarly, the chance constrained programming is used to deal with the uncertain factors in the model. Finally, the particle swarm optimization algorithm is improved to verify the validity of the model in the IEEE 30 system with wind power. This work is supported by Scientific Research Fund of Sichuan Provincial Education Department (No. 18ZB0566).