An exemplary method for driving a display device is provided. At least one set of input signals is received. Finding the original signals being the same with the input signals in the signal transforming table is executed. The pixel driving signals is outputted. If at least one of the found second and third original signals is equal to zero, and the found first original signal is equal to neither zero nor maximal gray scale, at least one of the outputted second and third sub-pixel driving signals, and the outputted fourth sub-pixel driving signal are equal to zero. Then, at least one of the pixels of the pixel array is driven by the outputted pixel driving signals. The input signals is transformed into the pixel driving signals by use of the signal transforming table, thereby saving the cost and improving the displaying quality.