A system for enhancing image sharpness includes a minimum unit, a maximum unit, a subtraction unit, a local mean unit, a sharpness calculation unit and a sharpness processing unit. The minimum unit receives pixels in a local area of an image to output a minimum luma value. The maximum unit receives the pixels in the local area of the image to output a maximum luma value. The subtraction unit subtracts the minimum luma value from the maximum luma value to generate a difference value. The local mean unit calculates an average of the luma values in the local area to generate a local mean value. The sharpness calculation unit calculates a sharpness factor for a pixel based on the difference value and an adjustable coefficient. The sharpness processing unit performs a sharpness processing on the pixel according to the sharpness factor and the local mean value.