A touch display system includes: a display driver integrated circuit (IC) configured to drive a display panel; a touch screen controller configured to drive a touch screen panel; a driving voltage generator configured to provide driving voltages to the display panel, the display driver IC, and the touch screen controller; and a ground modulation device configured to receive a driving signal, which is used to drive the touch screen panel and periodically swings between a first reference voltage level and a second reference voltage level, from the touch screen controller, configured to generate a modulated ground voltage, which periodically swings between the first reference voltage level and the second reference voltage level, based on the driving signal, and configured to provide the modulated ground voltage to the display panel, the display driver IC, and the touch screen controller