The present invention provides an image display method applied to an augmented reality (AR) system which positions a virtual object by a marker image. The image display method includes that: a reality image is acquired, wherein the reality image includes a first image where the marker image is positioned and a second image, and the marker image includes a known pattern; the first image in the reality image is replaced with an extending image of the second image on the basis of a relationship between the known pattern and the first image to generate a display image; and the display image is displayed. Therefore, the condition that an AR image includes the marker image and thus the whole image looks unnatural may be avoided. In addition, the AR system using the foregoing method is also provided.