The present invention discloses an information display system automatically adjusting the projection area and a method thereof. The method comprises steps: using a detection module to capture images of a driver and measure a distance between the detection module and the driver; recognize facial features of a driver (including a position of the driver's eye, a rotation angle of the driver's face, and a direction the driver fixates) to estimate a required displacement of the projection area on the windshield (i.e. the region inside the visual field of the driver); moving or rotating the projection device according to the required displacement of the projection area to make the projection device project images of driving information onto a correct region on the windshield.