An optical touch system includes a non-visible light source, a screen, a first and second polarizing elements, and an optical detector. The non-visible light source emits a non-visible beam. A part of the non-visible beam passes through the screen disposed in a light path of the non-visible beam. The touch object reflects the part of the non-visible beam into an object beam when a touch object approaches or touches the screen, and the object beam passes through the screen. The first polarizing element is disposed in the light path of the non-visible beam and between the non-visible light source and the screen. The optical detector is disposed in a light path of the object beam, and senses the object beam. The second polarizing element is disposed in the light path of the object beam passing through the screen and between the screen and the optical detector.