A pre-coding method and system and a method for constructing pre-coding codebook are disclosed, including: a transmitting end and a receiving end storing information of a pre-coding codebook together, the receiving end selecting a codeword from the pre-coding codebook according to an estimated channel matrix and feeding back a serial number of the codeword to the transmitting end, and the transmitting end finding out the codeword according to the serial number and pre-coding, by using the codeword, a symbol block sent to the receiving end; wherein, at least eight codeword vectors or column vectors in at least eight codeword matrixes in the pre-coding codebook are obtained based on 8-dimensional vectors selected from a 8-dimensional vector set, and this 8-dimensional vector set is obtained by calculating from the part or all of 4-dimensional vectors in u1, u2, u3, u4, u5, u6, u7, u8, s, m, n.