A channel state information feedback method and an apparatus to flexibly feed back channel state information, to implement balance between feedback overheads and feedback precision of the channel state information. The method includes: sending a media access control (MAC) frame, where the MAC frame includes a processing mode bitmap, every n bits in the processing mode bitmap correspond to one feedback unit, and a value of the n bits is used to indicate a processing mode of channel state information of the corresponding feedback unit; and receiving a beamforming report, where the beamforming report includes one or more feedback fields, each feedback field corresponds to one feedback unit, the feedback field includes channel state information of the corresponding feedback unit, and the channel state information included in the feedback field is processed in a processing mode indicated by the processing mode bitmap.