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, 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.