A method for constraining a codebook subset, comprising steps of: measuring, by a network side device, an uplink signal transmitted by a User Equipment, UE, so as to obtain a horizontal azimuth angle or a vertical azimuth angle of the UE; calculating, by the network side device, an array response vector correlation coefficient between each matrix in each matrix set for constructing a codebook and the horizontal azimuth angle or the vertical azimuth angle, comparing the array response vector correlation coefficient with an array response vector correlation coefficient threshold, and determining whether or not the matrix is available in accordance with a comparison result; determining, by the network side device, codebook subset constraint parameters for all or parts of matrix sets for constructing the codebook respectively in accordance with a determination result of the determining whether or not the matrix is available in accordance with the comparison result, each codebook subset constraint parameter indicating an available matrix in a corresponding matrix set; and transmitting, by the network side device, the determined codebook subset constraint parameters to the UE, wherein the available matrix is a matrix used for generating the active precoding matrices among the matrix sets for constructing the codebook, the active precoding matrices in the codebook are determined in accordance with the available matrices in each matrix set by: with respect to each precoding matrix in the codebook, determining whether or not all matrices for generating the precoding matrix are available, and determining the precoding matrix where all the matrices are available as the active precoding matrix; or with respect to each precoding matrix in the codebook, determining whether or not there is at least one available matrix in the matrices for generating the precoding matrix, and determining the precoding matrix where there is at least one available matrix as the active precoding matrix. measuring, by a network side device, an uplink signal transmitted by a User Equipment, UE, so as to obtain a horizontal azimuth angle or a vertical azimuth angle of the UE; calculating, by the network side device, an array response vector correlation coefficient between each matrix in each matrix set for constructing a codebook and the horizontal azimuth angle or the vertical azimuth angle, comparing the array response vector correlation coefficient with an array response vector correlation coefficient threshold, and determining whether or not the matrix is available in accordance with a comparison result; determining, by the network side device, codebook subset constraint parameters for all or parts of matrix sets for constructing the codebook respectively in accordance with a determination result of the determining whether or not the matrix is available in accordance with the comparison result, each codebook subset constraint parameter indicating an available matrix in a corresponding matrix set; and transmitting, by the network side device, the determined codebook subset constraint parameters to the UE, wherein the available matrix is a matrix used for generating the active precoding matrices among the matrix sets for constructing the codebook, the active precoding matrices in the codebook are determined in accordance with the available matrices in each matrix set by: with respect to each precoding matrix in the codebook, determining whether or not all matrices for generating the precoding matrix are available, and determining the precoding matrix where all the matrices are available as the active precoding matrix; or with respect to each precoding matrix in the codebook, determining whether or not there is at least one available matrix in the matrices for generating the precoding matrix, and determining the precoding matrix where there is at least one available matrix as the active precoding matrix. with respect to each precoding matrix in the codebook, determining whether or not all matrices for generating the precoding matrix are available, and determining the precoding matrix where all the matrices are available as the active precoding matrix; or with respect to each precoding matrix in the codebook, determining whether or not there is at least one available matrix in the matrices for generating the precoding matrix, and determining the precoding matrix where there is at least one available matrix as the active precoding matrix.