This invention relates to a Liquid crystal display and its shift buffer unit, which comprises a first/second switch both with corresponding input port, control port and output port, and a level conversion circuit. Wherein, the second control port couples to both the first output port and the conversion circuit; when enabling the first switch, the first input port receives the input signal to let the second control port output the first clock signal to the scan signal line; when being enabled, the conversion circuit converts the voltage of the second control port into the second voltage to close the second switch.