The invention relates to a graduation device for detecting the surface shape of an aspheric optical element, in particular to a graduation device for accurately controlling the displacement of a rotation angle. The invention provides a graduation device for accurately controlling the displacement of a rotation angle, which can feed back and compensate movement quantity and accurately control angular displacement in real time. The graduation device comprises a control system and a graduation device, wherein the control system is provided with an industrial personnel computer, an interface circuit board, a servo amplifier, a servo motor, an angular coder and a numeral display meter of the coder; and the graduation device is provided with a base, an upper bearing base, a main shaft, a motor base, a deep groove ball bearing, a main shaft synchronous pulley, a motor synchronous pulley, a synchronous belt, a rotary disk and a clamp.