The present invention provides a protective circuit, employed to protect a liquid crystal display, and the liquid crystal display includes a display panel and a level translator providing a clock signal to the display panel through an output line, and the protective circuit includes a first transistor, a detection circuit and a controller coupled to both the first transistor and the detection circuit, and the first transistor is electrically coupled to the detection circuit and the output line, and the clock signal is outputted to the display panel through the first transistor, and the detection circuit detects the clock signal and determines whether the clock signal is normal or not, and as the clock signal is abnormal, the controller controls the level translator to stop outputting the clock signal to the display panel.