A liquid crystal display apparatus, a source driver, and a method for controlling polarity of driving signals thereof are provided. The source driver includes a signal receiving interface, a decoder, and a controller. The signal receiving interface receives an image data stream or a data input/output indication signal. The decoder obtains polarity controlling information from the image data stream or the data input/output indication signal. The controller receives the polarity controlling information and decides driving polarities of a plurality of source driving signals generated by the source driver according to the polarity controlling information.