Abstract: High-power ultrasonic motors are commonly designed with the sandwich Langevin-type stator structure, which generates the complicated electrical-vibration-thermal two-way coupling dynamics under excitation of high frequency and voltage, bringing challenges in loss mechanism analysis and rapid-accurate temperature rise prediction. An impedance electromechanical equivalent circuit taking into account the electrical-vibration-thermal two-way coupling effect and a 3D thermal network topology are constructed based on the circuit viewpoint, to characterize the two-way coupling relationship between the electrical, mechanical branches and thermal network through the temperature-dependent impedance parameters and the inherent electromechanical coupling features of equivalent circuit, thereby establishing the accurate calculation model of the electrical-vibration-thermal two-way coupling losses. Furthermore, an adaptive time step coupling solving method is adopted to avoid solving the thermal network model too often, which can remarkably improve the computational efficiency. Simulation and experimental analysis validate the proposed model, upon which the influencing mechanism of the electrical-vibration-thermal two-way coupling effect on the stator losses is analyzed in depth.