An apparatus for adjusting a width of a rail mechanism is disclosed. The rail mechanism includes a fixed rail and a movable rail parallel with each other. The apparatus for adjusting the width includes: a base configured to be provided thereon with the fixed rail; a first guide rail provided on the base and configured to be installed with the movable rail, the movable rail being movable towards or away from the fixed rail along an axial direction of the first guide rail; a moving distance acquiring module configured to acquire a moving distance required for the movable rail to move from an initial position to a working position; and a driving assembly detachably connected with the movable rail and configured to drive the movable rail to move from the initial position to the working position based on the moving distance.