The analysis and calculation of dynamic energy flow for different energy forms are the basic work for the coordinated dispatching and operation of multi‐energy networks (MENs). A universal mathematical description of energy transfer is proposed based on the concept of intensity quantity and extensive quantity in thermodynamics. This paper derives the unified energy dynamic transfer equations of the electrical energy, incompressible viscous fluid, compressible gas, and heat transfer, that is, a generalised wave equation is established with the distributed parameters that characterise energy dissipation, storage and conductivity. Furthermore, the finite difference method is adopted to calculate the dynamic energy flow that varies with time and space. In the case analysis, the independent solution is firstly performed under four designed cases, and then the MEN composed of heat and gas is jointly solved. The calculation example verifies the feasibility and effectiveness of the proposed method.