A touch projection system includes a light source device, a micromirror device, and an image-capturing device. The micromirror device can provide three reflection directions. The micromirror device can selectively reflect projection light emitted by the light source device in one of the reflection directions to project the reflected projection light onto a screen to form an image. The micromirror device also can reflect image light from the screen in another one of the reflection directions. Further, the micromirror device can reflect the image light from the screen in the other one of the reflection directions, which has a larger deflection angle, to be received by the image-capturing device, for example for determining a touch operation performed on the screen. Thereby, the limitation of structural interference by other components to the image-capturing device is reduced, so that the touch projection system can be assembled in a compact configuration.