Provided are an electric brake system and an operating method thereof. The electric brake system includes a master cylinder to discharge a pressurized medium in accordance with displacement of a brakepedal, a simulation device to provide a driver with a pedal feeling, a hydraulic pressure supply device to generate a hydraulic pressure by operating a hydraulic piston in accordance with an electrical signal output in response to the displacement of the brake pedal, and a hydraulic control unit to control a hydraulic pressure of the pressurized medium supplied to each wheel cylinder. The electric brake system may perform a normal mode, an abnormal mode, and an inspection mode.