An optical system is provided. The optical system includes an optical member driving mechanism and an image sensor. The optical member driving mechanism includes a movable portion, a fixed portion and a first driving assembly. The movable portion is configured to connect an optical member, and the optical member has an optical axis. The movable portion is movable relative to the fixed portion. The first driving assembly drives the movable portion to move relative to the fixed portion. The image sensor is disposed to correspond to the optical member, and the optical axis passes through the image sensor.