A method includes: sending, by an access point AP, a channel measurement trigger frame TF-S to at least two stations STAs, where the TF-S is used to trigger the at least two STAs to send null data packets NDPs used for uplink channel measurement, the TF-S includes parameter indication information of a transmission parameter used by each STA to send theNDP, and the parameter indication information is used by the STA to determine the transmission parameter and a transmission time; and receiving, by the AP, an NDP sent by each of the at least two STAs based on a corresponding transmission parameter of the STA at a transmission time corresponding to the STA, and performing channel measurement, where there is no interframe gap between NDPs sent by any two adjacent STAs of the at least two STAs.