<p>Under constant-power charge and discharge conditions, both the motor rotational speed and current change rapidly, making it difficult to accurately calculate the temperature rise of the flywheel energy storage motor (FESM). To balance accuracy and efficiency, this paper proposes a temperature rise calculation method for variable-speed constant-power FESM based on steady-state temperature rise of an equivalent rotational speed point. First, the variable-speed constant-power operation process of FESM is introduced. Next, a dynamic loss model of FESM varying with rotational speed under constant power operation conditions is established. Then, the equivalent rotational speed point corresponding to the average loss of FESM is derived. Besides, taking a flywheel energy storage system as an example, the steady-state temperature rise at the equivalent rotational speed is calculated. Finally, the effectiveness of the proposed method is verified through finite element transient thermal simulation and prototype experiments. The results indicate that the maximum error of the proposed method is only 5.6%, observed in the winding component. In addition, it takes 2&#xa0;min to conduct the simulation by the proposed method and more than 10&#xa0;h for the transient simulation, reducing the time by 99%. Therefore, it can provide a reference for the thermal design of FESM.</p>