A liquid crystal display and a gate driver thereof are disclosed. The gate driver comprises a first output unit, a second output unit, a first counter, a second counter and a multiplex unit. The first counter counts a clock to control the first output unit to output odd gate driving signals according to a first start signal and a polarity signal. The second counter counts the clock to control the second output unit to output even gate driving signals according to a second start signal and the polarity signal. The multiplex unit selectively outputs the polarity signal to the first counter or the second counter.