A de-interlacing system includes a motion adaptive de-interlacer, a horizontal motion estimation device, a horizontal motion compensation device, a vertical motion detection device, a multiplexer, and a film signal detector. The film signal detector receives an input signal and decides whether the input signal is a video stream or a film stream to thereby select an output from the motion adaptive de-interlacer or the horizontal motion estimation and compensation device. Thus, a de-interlacing output has stable and smooth edges when a video stream is inputted, and the motion judder phenomenon is reduced when a film stream is inputted.