Under the background of increasing penetration of new energy in the power grid and the emergence of flexible load as a means of regulation, an appropriate dispatching mode is selected to enable a large number of distributed load resources to participate in the power grid regulation. This mode can help achieve the goals of peak shaving and valley filling and smoothing the load curve. Based on the cooperative control structure of load aggregator model, the load resources including electric vehicle, air conditioning load and energy storage equipment are aggregated, and the day ahead economic scheduling model is established. In the cluster internal control of load aggregator, considering the scheduling potential of equipments, a state queue priority algorithm based on margin index is proposed to realize partial load priority response. Finally, the simulation example shows that the load aggregator participates in the day ahead collaborative dispatching operation plan of the power system, and verifies the feasibility of the optimization method and regulation strategy.