The invention discloses a device for accurately detecting a mechanical part hole by using a magnetostrictive sensor. The device mainly includes a grip mounted on the bottom of a working chamber, the working chamber and two displacement devices mounted on the left and right ends of the working chamber, respectively. The displacement amount of a displacement device is accurately measured by the principle of magnetostrictive displacement, and the displacement device is in direct contact with parts when the distance between holes of the mechanical parts is measured, so that a movable magnetic ringfor measuring is not in direct contact with the sensor, so as not to be rubbed or worn, the service life is long, the environment adaptability is strong, the reliability is high, the safety is good,and the device facilitates automatic work of a system and can work normally even in a harsh industrial environment. An operator only needs to add a measurement result and the thickness of the top of the displacement device up to obtain accurate data of the hole diameter of the parts to be measured. Moreover, the device is simple in operation, novel in structure and convenient to use by the operator.