1. An image composition system, comprising: an image capturing unit, configured for capturing at least one first image of a real object; a depth information generating unit, disposed on the image capturing unit and configured for measuring a depth information between the depth information generating unit and the real object; a computing unit, receiving the at least one first image and the depth information, performing a computation of removing a noise caused by a moving object other than the real object from the received depth information by (1) obtaining a skeleton model of a figure from a depth map while removing an area where the skeleton model exists from the depth map, and (2) utilizing the depth maps generated at different times to extract and remove areas relating to the moving object, and computing a moving trajectory of the image capturing unit; and a composition unit, compositing the at least one first image and a second image of a virtual scene so as to achieve a composited result while displaying the composited result on a display unit.