There is provided a capacitive touch system including a gain control unit sequentially receiving a plurality of digital detected signals of a detection frame. The gain control unit includes a gain buffer and a control circuit. The gain buffer is configured to store a current gain sheet. The control circuit calculates a first gain sheet according to a setpoint and the digital detected signals of the detection frame, compares a current roughness of the current gain sheet with a first roughness of the first gain sheet and replaces the current gain sheet in the gain buffer by the first gain sheet when the first roughness is flatter than the current roughness.