A high-sensitivity in-cell touch display device has a common voltage and sensing electrode layer including a plurality of common voltage and sensing electrodes, each corresponding to at least one pixel electrode. A touch circuit is provided with a touch-dedicated power supply circuit, and a common voltage and sensing electrode is used as a common node of the touch circuit and a display circuit, so that there is no current loop between the touch circuit and the display circuit. Reflection electrodes are further provided to reduce parasitic capacitance between the common voltage and sensing electrodes and to improve the sensing distance. The display operation and the touch sensing operation can be performed on different areas in parallel to increase respective efficiencies of the display and touch sensing operations.