The present application provides an in-cell touch display panel, a driving method thereof, and a display device. At least two sub-pixels are a sub-pixel group, cathode layers of different sub-pixel groups are independent of each other, which is equivalent to that the cathode layer set as a whole surface in the prior art is segmented, one sub-pixel group corresponds to one segmented cathode layer, cathode layers of respective sub-pixel groups are connected through conductive lines to the driver chip, so that the cathode layer is reused as a self-capacitive touch control electrode, the driver chip detects a capacitance variation of the cathode layer through the conductive line corresponding thereto to determine a touch location, thus achieving the touch control function. In the in-cell touch display panel, signals outputted by the driver chip to respective signal terminals of a sub-pixel circuit and the cathode layer in a fourth stage are obtained by superimposing the same touch scanning signal on basis of signals outputted to the respective signal terminals and the cathode layer in a third stage, so that the operating state of each module in the sub-pixel circuit is the same as that in the third stage, which ensures normal display, therefore an in-cell touch display panel based on OLED panel is achieved.