Feedback channel state information feedback method, a terminal, a base station and a communication system

The present invention discloses a kind of channel state feedback information determining method, a terminal, a base station and a communication system. The method of: measuring a channel state, a measurement result; when the rank indicator (RI) is 2, and the measurement result according to the precoding codebook matrix model code precoding matrix W formed; and based on the precoding matrix, a channel is formed state feedback information.