System and method for enhancing saturation of rgbw image signal

A system and a method for enhancing the saturation of an RGBW image signal are provided to increase the saturation of unmixed color by increasing the brightness of backlight and reducing the brightness of a white sub pixel at an RGBW display. An image signal classifier(103) uses image classification parameters depending on the brightness and saturation of an image signal to classify each frame of image signal according to image classification unit. A backlight brightness controller(104) increases the brightness of the backlight as to a frame which is the target of saturation increase, and a white sub pixel controller(105) reduces the brightness of the white sub pixel of the image signal by corresponding to the increased amount of the backlight brightness. An RGBW image signal converter(101) converts an RGB image signal into an RGBW image signal.