The invention provides an image display system and an image presenting method thereof. The image display system includes a display apparatus and an image presenting apparatus. The display apparatus receives an output image signal and generates an image frame. The image presenting apparatus obtains a plurality of input image signals from a plurality of image sources and generates an output image signal. The image presenting apparatus provides the output image signal to a display apparatus. The image presenting apparatus receives a preview request to simultaneously and timely present the input image signals of all the image sources in a preview block of the image frame. Also, the image presenting apparatus further receives a select request to generate the output image signal according to at least one of the input image signals that is selected.