A method applied to a signal synchronization system, a system, a stylus, and an electronic device. The system includes a stylus and an electronic device. The electronic device supports a first refresh rate and a second refresh rate. The method includes: after an electronic device is wirelessly connected to a stylus, the electronic device samples a downlink signal from the stylus based on a third refresh rate, where the third refresh rate is equal to a first refresh rate or a second refresh rate; and the stylus sends the downlink signal to the electronic device based on the third refresh rate, and samples an uplink signal from the electronic device at a fourth refresh rate, where the fourth refresh rate is the least common multiple of the first refresh rate and the second refresh rate.