A system for transmitting and receiving Channel State Information (CSI) is provided, in which a terminal receives a pilot signal transmitted from a transmitter, the terminal estimates CSI of part of downlink channels based on the received pilot signal, the terminal superposes the CSI of part of downlink channels onto a uplink sounding signal orthogonally, and transmits them together; the transmitter obtains the CSI of the rest part of downlink channels by estimating the uplink sounding signal, the transmitter performs orthogonal de-multiplexing on the received signal to obtain the CSI of the part of downlink channels, the transmitter, by using the CSI of the two parts of downlink channels, pre-codes downlink data and transmits it to the terminal.