A source driving device, a polarity reversal control method thereof, and a liquid crystal display device. In the source driving device, a polarity signal control unit is added, and an output terminal of the polarity signal control unit is connected to control terminals of a first channel selection circuit and a second channel selection circuit in a positive-negative polarity reversal control unit, respectively. Polarity reversal condition of the polarity reversal control signal outputted by the polarity signal control unit is controlled using a trigger control signal inputted to a control terminal of the polarity signal control unit.