A method for transmitting channel state information, comprising: determining (S51), by a UE, a basis matrix according to a candidate beam vector set, wherein the basis matrix is a matrix of N beam vectors in the candidate beam vector set, and N is a positive integer; determining (S52), by the UE, a combination coefficient matrix according to the basis matrix and a channel state parameter, wherein the combination coefficient matrix is obtained by calculating from the basis matrix and the channel state parameter and quantizing the calculated result; and feeding (S53), by the UE, an identifier of the basis matrix, and the combination coefficient matrix back to a base station, so that the base station determines a pre-coding matrix for downlink transmission with the UE according to the basis matrix and the combination coefficient matrix; wherein determining (S51), by the UE, the basis matrix according to the candidate beam vector set comprises: selecting, by the UE, T beam vectors from the candidate beam vector set, wherein T is an integer more than N; and selecting N beam vectors from the T beam vectors, and determining a matrix of the selected N beam vectors as the basis matrix; wherein when the UE selects T beam vectors from the candidate beam vector set, and selects N beam vectors from the T beam vectors, feeding, by the UE, the identifier of the basis matrix back to the base station comprises: feeding, by the UE, identifiers of the T beam vectors back to the base station as first-level identification information, and feeding, by the UE, identifiers of the N beam vectors in the T beam vectors back to the base station as second-level identification information. determining (S51), by a UE, a basis matrix according to a candidate beam vector set, wherein the basis matrix is a matrix of N beam vectors in the candidate beam vector set, and N is a positive integer; determining (S52), by the UE, a combination coefficient matrix according to the basis matrix and a channel state parameter, wherein the combination coefficient matrix is obtained by calculating from the basis matrix and the channel state parameter and quantizing the calculated result; and feeding (S53), by the UE, an identifier of the basis matrix, and the combination coefficient matrix back to a base station, so that the base station determines a pre-coding matrix for downlink transmission with the UE according to the basis matrix and the combination coefficient matrix; selecting, by the UE, T beam vectors from the candidate beam vector set, wherein T is an integer more than N; and selecting N beam vectors from the T beam vectors, and determining a matrix of the selected N beam vectors as the basis matrix; wherein when the UE selects T beam vectors from the candidate beam vector set, and selects N beam vectors from the T beam vectors, feeding, by the UE, the identifier of the basis matrix back to the base station comprises: feeding, by the UE, identifiers of the T beam vectors back to the base station as first-level identification information, and feeding, by the UE, identifiers of the N beam vectors in the T beam vectors back to the base station as second-level identification information. <EOS>