Due to the limitation that the branch power exceeds the capacity of the transmission line, the transmission congestion problem will occur in some time periods of the transmission network. With the demand side response and a large number of distributed energy access to the distribution network, it is possible to coordinate the controllable resources in the transmission network and the distribution network to solve the transmission congestion problem. Aiming at the problem that the demand side response resources are scattered and difficult to negotiate the compensation price, a bi-level optimization congestion scheduling strategy based on dynamic integration of flexible resources in distribution network is proposed. Under this strategy, the transmission network layer takes the minimum congestion cost as the goal, and optimizes the adjustment scheme of the generator set and the node price. The active distribution network layer dynamically integrates the flexible resources of the distribution network through the load characteristics and the node price. Through the interaction and coordination between the two layers, the optimal congestion scheduling scheme is obtained, and the transmission and distribution coordination solves the congestion problem. Based on the modified IEEE-39 experimental system, the effectiveness of the proposed strategy is verified by simulation.