A channel state information transmission method, where a responder receives a channel measurement signal sent by an initiator by using one or more transmit antennas, and the responder sends a feedback frame to the initiator based on the channel measurement signal. The feedback frame includes information used to indicate a transmit antenna subset of the initiator and one or more channel state information blocks of a channel between the corresponding transmit antenna subset of the initiator and the responder, where the transmit antenna subset is determined from one or more transmit antennas by using which a channel measurement signal is sent.