A liquid crystal display (1) includes a liquid crystal panel (12) including a number of thin film transistors (123), a timing control circuit (16), a common voltage generating circuit (14) and a gamma circuit (13). The timing control circuit is configured for generating timing signals. The common voltage generating circuit is configured for generating a common voltage. The gamma circuit is configured for generating gray-scale voltages. When the liquid crystal panel is powered on, the common voltage is applied to the liquid crystal panel and reaches a predetermined value before the gray-scale voltages are applied to the liquid crystal panel and comes to predetermined values. And when liquid crystal panel is powered off the common voltage and the gray-scale voltages drops to 0V simultaneously by control of the common voltage generating circuit and the gamma circuit with the thin film transistors switched on.