The high proportion of renewable energy significantly improves the interactive capability of the distribution system, but also raises increasingly prominent uncertainty issues. In order to enhance the energy supply capacity and flexibility of distributed resources, a quantitative aggregation model of resources based on operating states and an optimal scheduling strategy considering the operational flexibility of the distribution system are proposed to characterize the participation of multiple resources as an aggregator in power market scheduling. Firstly, this paper establishes a quantitative model of resource flexibility that considers the operational characteristics and net load demand to fully exploit the dispatchable potential of distributed resources. Secondly, the aggregator model based on the power feasible domain and the equivalent aggregation model of distributed resource cost function are established to improve the synergistic operation and overall responsiveness of resources. Finally, considering the supply and demand balance constraints of the distribution system’s flexibility, an optimal scheduling model is established with the objective of optimal system operation costs to improve resource utilization efficiency and system operation flexibility. The feasibility and effectiveness of the proposed model and scheduling strategy are verified by simulation.