An image alignment method includes: fetching at least two images; calculating a relative displacement between those adjacent images by utilizing a phase correlation algorithm; calculating an absolute displacement between any one of those images and the first image of those images; and computing a common area of those images by utilizing the relative displacement and the absolute displacement, then deleting remainder portions of the image excluding the common area. In the present invention, the phase correlation algorithm can be utilized to process numerous noise signals so as to get a higher precision of the image alignment.