A source driving device for a display system includes a receiving module, for receiving display data; a register module, for sorting pixel data included in the display data to generate sorted pixel data; a latch module, for outputting sequenced display data to the level shifting module; a level shifting module, for adjusting the sequenced display data from a low voltage range to a medium voltage range; a converting module; for converting the sequenced display data to analog display voltages; a buffer module, for generating a plurality source driving signals according to the analog display voltages; and an output switching module, for outputting the plurality source driving signals to a display device of the display system operating in a high voltage range; wherein circuit components in the source driving device operating in different voltage ranges have different gate oxide thicknesses.