Large-scale wind power poses serious challenges to optimal system dispatching. The traditional optimal dispatching models for a wind farm integrated grid are highly dependent on an accurate wind power probability distribution or a high-precision ranging of wind power fluctuation. This may cause calibration problems and wind curtailment when the uncertainty of wind power exceeds the expected value. In order to cope with the problem of accommodation of wind power, a theory of security region is introduced to analyze the relationship among the security region, steady-state security distance and the uncertainty of wind power. An optimal dispatching model for a wind farm integrated grid considering steady-state security distance is proposed. The simulation results of the IEEE39-bus system show that this proposed model has a more robust and stronger operability in the face of low-precision wind power prediction.