In recent years, the whole society's electricity demand showed a sustained and rapid growth trend. The power supply is difficult to meet the demand. During the load peak period in summer, the proportion of air-conditioning load is as high as 30–50%. This kind of load will lead to further widening of the peak-valley difference and bring hidden danger to the operation of the power grid. The interaction between users, load aggregator and grid dispatch centre are introduced first and then, the design contract details between the user and load aggregator which has great significance on practical applications. Two dispatching models based on load aggregator and direct load control are put forward, which incorporates the electric excitation and electricity price response, to ensure safe and stable operation of power grids during the peak period. On the basis of grid stable operation, achieving costs optimal. Finally, solving results show that the coordinated dispatching strategy the authors proposed could not only effectively reduce the peak load of the system, but could also fast and precisely dispatch loads when system faults occur.