Provided are a method for channel information feedback in a multi-antenna system, and a terminal. The method comprises: a terminal receives CSI-RSs of M ports sent by a base station, and performs estimation according to the CSI-RSs to obtain M-dimensional downlink channel information; the terminal uses a transformation function Fk to perform a linear transformation on the M-dimensional downlink channel information, and obtains Nk-dimensional kth type channels, wherein k is greater than or equal to 1 and less than or equal to K, M≥Nk, and K≥1; the terminal uses a preset Nk-dimensional codebook to respectively perform channel information quantisation on the kth type channels, and determines a corresponding precoding matrix and precoding matrix indicator information (PMIk); the terminal selects S type channels from within K type channels, and feeds index numbers of the selected channels and corresponding PMI back to the base station.