An in-wheel drive system includes a hub, a driving motor, a rotor support fixed to a rotor of the driving motor on the inner radial side of the rotor, and planetary gear reducers. The planetary gear reducer comprises a sun gear shaft, a planetary gear, a ring gear, and a planetary gear carrier, wherein the sun gear shaft is fixed to the rotor support on the outer radial side of the hub, and the planetary gear carrier is fixed to the hub. A driving force/torque is transmitted to the hub via the rotor, the rotor support, the sun gear shaft, the planetary gear, and the planetary gear carrier. The in-wheel drive system removes the need for a conventional transmission half axle, differential, and other transmission parts, shortens the transmission chain, is conducive to the vehicle layout design, and can easily implement torque vector control.