A source driver of an LCD includes a shift register, a set of data latches, and a detection circuit. The shift register includes a plurality of flip-flops for transmitting a start signal. The set of data latches transmits the display data signal according to output signals of the corresponding flip-flops. When the start signal is recognized as a black insertion signal, the detection circuit resets the shift register, and drives the set of data latches to output the black data signal, and transmits the black insertion signal to the next source driver.