The invention discloses an all-vanadium redox flow battery energy storage system equivalence method based on electric-thermal coupling. The method comprises: 1, performing modeling on electrical characteristics of a VRB according to a second-order resistance-capacitance network; 2, performing parameter identification by using a particle swarm algorithm; 3, analyzing the heat production condition of each module in the operation of the battery; 4, analyzing the heat transfer process of the VRB system; 5, based on an electric-thermal ratio fitting principle, a heat transfer path being equivalent; and 6, combining all the states obtained in the step 2 and the step 5 to obtain a complete state space equation of the VRB energy storage system electric heating coupling model. According to the method, the electrical characteristics and the heat generation characteristics of the VRB energy storage system during operation and the coupling relation between the electrical characteristics and the heat generation characteristics are comprehensively considered, the charge state, the terminal voltage and the temperature states of all parts of the battery can be accurately predicted, and safe and stable operation of the VRB is effectively guaranteed.