This application provides a signal decoding method, a decoding circuit, and a stylus. In one example, a to-be-measured signal is sampled to obtain a plurality of sampled signals. The to-be-measured signal is a modulation signal that carries an interference signal. The modulation signal is sent by a touch panel of a terminal device. At least two edge signals in the to-be-measured signal are determined based on the plurality of sampled signals. The to-be-measured signal is decoded based on the at least two edge signals to obtain the modulation signal.