A power module assembly is disclosed and includes a package body, a first wiring layer, a capacitor, and a system bus set. The package body includes a first surface, a second surface and two switches connected in series to form a bridge arm between the first surface and the second surface. The first wiring layer is disposed on the first surface. The capacitor is connected in parallel with the bridge arm to form a first high-frequency loop. The system bus set includes a positive-electrode bus and a negative-electrode bus fanned out from the first surface, respectively. The projection of the positive-electrode bus or/and the negative-electrode bus on the first surface is at least partially overlapped with the projection of the two switches on the first surface. The bridge arm is electrically connected between the positive-electrode bus and the negative-electrode bus to form a second high-frequency loop.