This invention relates to an integrated electric drive system assembly and an electric vehicle to achieve light weight and integration of the assembly. The assembly comprises a speed reducer, a drivemotor, a high-voltage junction box, a motor controller, and a power supply module, wherein the speed reducer is arranged in a reducer housing; the drive motor is arranged in a stator housing, and thestator housing and the reducer housing share the same end cover; a transmission input shaft of the speed reducer and a rotor shaft of the drive motor pass through the end cover to be coaxially connected in a transmission manner; an electric control housing, the reducer housing and the stator housing are in plane distribution; the power supply module and the high-voltage junction box are arranged on the upper side in the electric control housing, the motor controller is arranged on the lower side in the electric control housing, and the high-voltage junction box is connected with the motor controller and the power supply module and supplies power to a compressor and a heater in the vehicle; the motor controller is connected to the drive motor; and the electric control housing is fixedly connected to the reducer housing and/or the stator housing.