A method for obtaining a precoding matrix indicator, characterized by comprising: obtaining a first rotation matrix according to first channel information; obtaining (102, 203) a first differential matrix according to the first rotation matrix and an instantaneous beam forming matrix or precoding matrix that is obtained currently and which reflects the current channel status; and quantizing, according to a first differential codebook, a pre-acquired first rank indicator, and preset quantization criteria, the first differential matrix to obtain a differential precoding matrix indicator; wherein the first channel information is a first long-term channel covariance matrix, obtaining the first rotation matrix according to the first channel information comprises: performing eigenvalue decomposition on the first long-term channel covariance matrix to obtain an eigen matrix of the first long-term channel covariance matrix, wherein the first long-term channel covariance matrix is obtained by averaging multiple channel matrixes obtained at a user equipment or an evolved node B, eNB, on a single or multiple subcarriers in a preset time period; and using the eigen matrix of the first long-term channel covariance matrix as the first rotation matrix; or wherein the first channel information is a reference precoding matrix indicator, the obtaining the first rotation matrix according to the first channel information comprises: if the reference precoding matrix indicator is orthogonal to columns of a precoding matrix corresponding to the pre-acquired first rank indicator and the rank is full, normalizing respective columns of the precoding matrix and using a normalized precoding matrix as the first rotation matrix; if the reference precoding matrix indicator is orthogonal to columns of a precoding matrix corresponding to the pre-acquired first rank indicator and the rank is not full, but a codebook corresponding to the reference precoding matrix indicator meets nesting characteristics, selecting a full-rank precoding matrix corresponding to the reference precoding matrix indicator, normalizing respective columns of the full-rank precoding matrix, and using a normalized full-rank precoding matrix as the first rotation matrix; or, if the first channel information is the reference precoding matrix indicator, the obtaining the first rotation matrix according to the first channel information comprises: normalizing respective columns of precoding matrixes corresponding to the reference precoding matrix indicator and the pre-acquired first rank indicator; and performing QR decomposition for a normalized precoding matrix to obtain the first rotation matrix. obtaining a first rotation matrix according to first channel information; obtaining (102, 203) a first differential matrix according to the first rotation matrix and an instantaneous beam forming matrix or precoding matrix that is obtained currently and which reflects the current channel status; and quantizing, according to a first differential codebook, a pre-acquired first rank indicator, and preset quantization criteria, the first differential matrix to obtain a differential precoding matrix indicator; wherein the first channel information is a first long-term channel covariance matrix, obtaining the first rotation matrix according to the first channel information comprises: performing eigenvalue decomposition on the first long-term channel covariance matrix to obtain an eigen matrix of the first long-term channel covariance matrix, wherein the first long-term channel covariance matrix is obtained by averaging multiple channel matrixes obtained at a user equipment or an evolved node B, eNB, on a single or multiple subcarriers in a preset time period; and using the eigen matrix of the first long-term channel covariance matrix as the first rotation matrix; or wherein the first channel information is a reference precoding matrix indicator, the obtaining the first rotation matrix according to the first channel information comprises: if the reference precoding matrix indicator is orthogonal to columns of a precoding matrix corresponding to the pre-acquired first rank indicator and the rank is full, normalizing respective columns of the precoding matrix and using a normalized precoding matrix as the first rotation matrix; if the reference precoding matrix indicator is orthogonal to columns of a precoding matrix corresponding to the pre-acquired first rank indicator and the rank is not full, but a codebook corresponding to the reference precoding matrix indicator meets nesting characteristics, selecting a full-rank precoding matrix corresponding to the reference precoding matrix indicator, normalizing respective columns of the full-rank precoding matrix, and using a normalized full-rank precoding matrix as the first rotation matrix; or, if the first channel information is the reference precoding matrix indicator, the obtaining the first rotation matrix according to the first channel information comprises: normalizing respective columns of precoding matrixes corresponding to the reference precoding matrix indicator and the pre-acquired first rank indicator; and performing QR decomposition for a normalized precoding matrix to obtain the first rotation matrix.