1. A method of providing augmented reality based on marker tracking technology, the method comprising: capturing an image by an image capturing unit; determining whether a quadrangle is present in the image; when the quadrangle is found in the image, determining whether the quadrangle is a marker in accordance with a marker definition; when the quadrangle is determined to be the marker, identifying an order of four vertex coordinates of a marker image and identifying an identity of the marker; determining a rotation state of the marker according to the vertex coordinates of the marker image and calculating a relative displacement between the marker and the image capturing unit; and combining a three-dimensional object to the image according to the relative displacement, the rotation state, and the identity of the marker to generate an augmented reality image.