This application provides a signal decoding method, a decoding circuit, and a stylus. One example method includes: sampling a to-be-measured signal based on a predetermined sampling rate to obtain a plurality of sampled signals, where the to-be-measured signal is a modulation signal that carries an interference signal, and the modulation signal is sent by a touch panel of a terminal device; determining at least two edge signals in the to-be-measured signal based on the plurality of sampled signals; and decoding the to-be-measured signal based on the at least two edge signals to obtain the modulation signal.