An optical touch system is disclosed. The optical touch system includes an optical touch apparatus, a control apparatus, and a rotating apparatus. When the control apparatus receives a mode switching signal, the control apparatus selects a corresponding specific using mode from a plurality of default using modes according to the mode switching signal. And, the specific using mode corresponds to a specific rotating angle. The rotating apparatus rotates the optical touch apparatus with the specific rotating angle to make the optical touch apparatus is rotated from a first location to a second location, so that a user can perform an input action via the optical touch apparatus according to the specific using mode.