As the regulating range is limited in the real-time dispatch, the security improvement is more prominent than the economic improvement for the real-time dispatch. Based on the preemptive goal programming and the steady-state security region estimation methods, this paper proposed a model for the real-time dispatch, in which the base-points and the participation factors of the AGC (Automatic Generation Control) units are co-optimized. The model has two goals. One is to maximize the ability of the power system to depress the load disturbances by maximizing the overlap region of the steady-state security region and the load variation region (named as the effective steady-state security region). The other one is to minimize the operating costs including the generation costs and the reserve costs. By setting the first goal as the preemptive goal, the economic dispatch results are obtained with respected to the maximized effective steady-state security region. Numerical tests demonstrate the effectiveness of the proposed approach.