The present application relates to the field of mobile communications, and in particular to a multi-antenna technology in a wireless communication system. Provided in the instant application are a channel state information (CSI) transmitting method, device and system. In said solution, a terminal device feeds a first rank and a first pre-coded matrix indication used for a public channel back to a base station, and feeds a second rank and a second pre-coded matrix indication used for a service channel back to the base station. The first pre-coded matrix instruction is used to indicate a first pre-coded matrix in a first pre-coded matrix set. The second pre-coded matrix instruction is used to indicate a second pre-coded matrix in a second pre-coded matrix set. The first pre-coded matrix set is different from the second pre-coded matrix set. The channel state information is obtained by means of different pre-coded matrix sets being used for public channels and service channels. The present invention is able to satisfy system requirements, while also saving bits that are fed back.