The technology of this application relates to a method including a first device constructing a ranging signal waveform through time reversal by using a channel impulse response of a channel between the first device and a second device or a received signal sent by the second device, to implement matching between a ranging signal and the channel, and the second device completing time of flight measurement based on a received signal by using a correlation operation, and determining, through sampling, whether a ranging process is interfered with, to implement integrity protection for the ranging signal. According to embodiments of this application, a receive end can have a capability of detecting whether a ranging process is interfered with, thereby ensuring integrity of a ranging signal without compromising ranging performance of a system.