A method and system for acquiring channel information are disclosed in the present document, wherein the method includes: a base station and a User Equipment (UE) jointly saving a first codebook and at least a second codebook, and the first codebook being used for channel information quantization in various scenarios; the UE performing feedback of at least 2 Precoding Matrix Indicators (PMIs) to the base station, wherein, one PMI corresponds to one code word in the first codebook, all the other PMIs respectively correspond to different code words in a second codebook used currently, and all the code words corresponding to the fed back PMIs are used for representing channel information of one or multiple or all subbands; and after receiving the PMIs fed back from the UE, the base station finding corresponding code words from the first codebook and the second codebook used currently, and acquiring the channel information.