In order to obtain the 3D temperature distribution of bulk acoustic wave (BAW) filter at a given power level quickly and efficiently, an electromagneticthermal coupled simulation method is proposed. Firstly, the thermal simulation model of the BAW filter is built and the electromagneticthermal coupled solution method is set. Then the electromagnetic model of the BAW filter is generated from the thermal simulation model to extract the conductor loss in the electromagnetic model of the BAW filter. Finally, the extracted loss is used as the heat source of the thermal simulation, and the 3D temperature distribution of the filter is obtained by electromagneticthermal coupled simulation. The simulation results show that among the 7 resonators in a BAW filter case, the first series resonator and the first parallel resonator are the hottest series resonator and the hottest parallel resonance respectively when the input power is 1 W. The hot spot temperature in the filter case is 81.472 ℃, which appears in the top electrode of the first parallel resonator; the cold spot temperature is 49 ℃, which appears in the piezoelectric layer of the third parallel resonator.