District heating networks (DHNs), due to their thermal storage capacity, can provide flexibility for integrated electricity and heat energy systems and improve wind power accommodation. However, the coordinated optimization of large-scale DHNs and integrated energy systems faces great challenges due to the large size and complexity of the DHN dynamic model. The combination of a single pipe’s dynamic equations and topological equations between pipes is so complex that the networks cannot be optimized globally; thus, only local optimization can be achieved. To improve the accuracy of coordinated optimization, this paper contributes to developing a lightweight dynamic model of a large-scale DHN based on the thermal-electrical analogy circuit model. First, a heat-transportation contribution matrix for each single pipe is proposed. Second, the matrix-form heat balance equations between pipes are established. Third, the temperature response between the DHN’s last outlet and the first inlet can be reflected by a coefficient matrix, which is obtained by multiplying all the heat-transportation contribution-matrix and heat balance matrices. Finally, a lightweight dynamic model of a large-scale DHN is established without any intermediate pipe variables. It is validated by the experiments, and the errors between the experimental and theoretical results are less than 5%.