A method and device for acquiring channel information are disclosed in the present invention, to solve a technical problem in the related art that the channel information cannot be fed back flexibly according to requirements. The method includes: for one subband, User Equipment (UE) acquires Rank Indicator (RI) information of a current channel, in which the RI information indicates a rank (ν) of the current channel, and ν is a positive integral number not greater than 8; the user equipment determines the quantity of the Precoding Matrix Indicator (PMI) information required to be fed back to a base station according to ν, and transmits the PMI information in said quantity and the RI information to the base station; the base station acquires the channel information of said subband according to the PMI information in said quantity and said RI information.