The present invention discloses a method, device, and system for transmitting channel information, pertaining to the field of radio communication. The method for obtaining channel information includes: transmitting, by a beamformer, a request for obtaining channel information to a beamformee within the duration of a current first TXOP; receiving a null feedback frame transmitted by the beamformee within the duration of the current first TXOP; within the validity period of the channel information, if the beamformer obtains a second TXOP, transmitting, within the second TXOP, a channel information indication frame to request the channel information, and receiving the channel information transmitted by the beamformee. The system includes a beamformer and a beamformee. The present invention saves the signaling resources of the beamformer and reduces the power consumption of the beamformee.