An image processing circuit and a method thereof. The image processing circuit includes a light sensor, an image control unit, a Gamma curve LUT, a backlight control unit and an image processing unit. The light sensor senses an intensity of ambient light and outputs an intensity signal. The image control unit receives an image signal and determines an image luminance value corresponding to a first image data of the image signal according to the intensity signal. The Gamma curve LUT outputs a luminance value signal corresponding to the image luminance value. The backlight control unit outputs a backlight luminance signal corresponding to the image luminance value. The image processing unit outputs a second image data corresponding to the first image data according to the luminance value signal and the backlight luminance signal.