The invention discloses a device for synchronously measuring the back electromotive force coefficient and the cogging torque of a motor. A servo motor is fixedly installed on a base plate, the two ends of a torque sensor are connected with the servo motor and a rotating shaft, a height adjusting structure is installed on the base plate, and a clamping structure is installed on the height adjustingstructure; a stator of a measured motor is fixed to the clamping structure, and the height adjusting structure adjusts the center height of the stator of the measured motor to enable the center height of the stator of the measured motor to be consistent with that of the measurement device; a rotor of the measured motor is connected with the rotating shaft, and the servo motor drives the rotor ofthe measured motor to rotate through the torque sensor and the rotating shaft; the rotating speed of the rotor of the measured motor is consistent with that of the servo motor, the rotor rotates uniformly, then the back electromotive force coefficient is obtained, the torque sensor measures the total torque to obtain the cogging torque, and the two completely independent motor performance tests are integrated; and measurement can be conducted before the motor is not assembled, unqualified parts can be replaced in time, and disassembly is avoided.