A method includes: sending, by an AP, a channel measurement notification message, where the channel measurement notification message includes a STA indication and a to-be-measured channel indication; receiving, by the AP, channel sounding signals sent by M STAs, where the M STAs that need to measure a channel are divided into W groups, N STAs in a same group simultaneously send channel sounding signals on a same sub-channel in the V to-be-measured sub-channels, the channel sounding signal includes a plurality of subcarriers, every Ng consecutive subcarriers are a group of subcarriers, each STA in each group occupies a subcarrier at a fixed location in each group of subcarriers, and subcarriers that are occupied by the N STAs in the same group and that are in a same group of subcarriers are different from each other.