The model of urban integrated energy dispatching system is a mathematical model used to describe the distribution of energy flow in the system, which has the characteristics of high accuracy, strong nonlinearity, and non-convexity. However, in the optimal power flow and other optimization problems, the traditional numerical solution algorithm cannot be directly applied. The strong nonlinearity and non-convexity of the system power flow model bring great difficulties to the solution of the optimization problem. Based on the input and output theory of cooling, heating, and power complementary energy, this paper studies the coupling energy relationship and power flow of various energy devices in an urban multi-source microgrid. It establishes the reliability index of the system energy supply, starting from the integrated energy system structure of low-carbon cities. A bi-level optimization model considering the constraints of energy supply reliability is constructed, which provides a basis for the subsequent establishment of the optimal allocation model.