An exemplary liquid crystal display (200) has a liquid crystal panel (240); a gate driving circuit (230) configured for scanning the liquid crystal panel; a data driving circuit (220) configured for providing a plurality of gradation voltages to the liquid crystal panel; a photo sensor (241) configured for measuring a luminance of ambient light and generating a corresponding optical signal; a luminance control circuit (231) for receiving the optical signal from the photo sensor and transferring the optical signal to a measurement signal; a timing control circuit (210) configured for controlling the gate driving circuit and the data driving circuit; and a backlight circuit (270) for driving a light source to emit light beams for illuminating the liquid crystal panel, according to the measurement signal from the luminance control circuit.