A touch system has a touch device and an input device. The touch system executes a first mode and a second mode at different times. In the first mode, the touch device transmits a modulation signal to drive the touch electrodes and to be used as an uplink signal. The input device receives the modulation signal. In the second mode, the touch device receives the downlink signal from the input device. Thus, the touch device does not have to transmit the driving signal and the uplink signal at different times. Then the time is saved for the rest work periods so that every work periods get longer length of time.