An optical system is provided and includes a fixed module, a movable module, a driving coil, a sensing unit and a driving assembly. The fixed module includes an outer frame, and the movable module includes an optical member holder, configured to hold an optical member. The sensing unit is configured to obtain information related to a first rotation angle of the holder when rotating around a first axis relative to the outer frame and a second rotation angle of the optical member holder when rotating around a second axis relative to the outer frame. The driving assembly is for driving the optical member holder to rotate around the first axis or the second axis according to the information related to the first rotation angle and the second rotation angle. The first axis or the second axis is perpendicular to an optical axis of the optical member.