In the field of communication technologies, a method and an apparatus for acquiring a Precoding Matrix Indicator (PMI) and a Precoding Matrix (PM) are provided. The method includes: acquiring a reference PMI and a differential PMI according to a first non-differential codebook and a first diagonal differential codebook, where codewords included in the first diagonal differential codebook form a diagonal matrix. The apparatus includes a PMI acquiring module. Acquiring a reference PMI and a differential PMI according to a non-differential codebook and a diagonal differential codebook can reduce the feedback overhead or improve the feedback precision; and the fact that codewords included in the diagonal differential codebook form a diagonal matrix can maintain amplitude characteristics (for example, a constant modulus characteristic, and a finite character set constraint characteristic) of elements of the non-differential codebook or facilitate power distribution among antennas.