1. A displaying method used in a transflective type display device whose pixel array has three basic-color sub-pixels and one enhancement sub-pixel, wherein there is a reflective area within the enhancement sub-pixel, the pixel array has a first selected pixel unit formed by any three sub-pixels selected from the abovementioned four sub-pixels, the displaying method comprises: providing an original image having an image data to the display device, wherein the image data comprises the data of the three basic-color sub-pixels; scaling down the resolution of the original image according to a second selected pixel unit consisting of the three basic-color sub-pixels and the enhancement sub-pixel for obtaining an adjusted image data when a backlight of the display device is turned off, wherein the adjusted image data comprises the data of the three basic-color sub-pixels; and calculating the driving value of the enhancement sub-pixel according to the adjusted image data for driving the enhancement sub-pixel; wherein the original image has a first resolution S 1 , the adjusted original image has a second resolution S 2 , and the relationship between S 1 and S 2 is expressed as: S 2 =(n/m)×S 1 , where n is the number of sub-pixels of the first selected pixel unit and m is the number of sub-pixels of the second selected pixel unit.