The present invention proposes a technical solution of codebook design which is suitable for antennas configured in a uniform circular array. Respective codewords in the designed codebooks have constant modulus, respective columns being orthogonal to each other and nested property. Based on the designed codebook, the invention further provides a method of determining a codeword in a base station of a MIMO communication system, the base station being configured with Nt antennas in a uniform circular array, wherein the method comprises the steps of receiving codeword index information from a user equipment; and determining a target codeword corresponding to the codeword index information from a set of codebooks according to the codeword index information,wherein the set of codebooks comprises Nt codebooks corresponding respectively to respective ranks and the Nt codebooks are determined based upon a codebook of rank 1 and a Nt×Nt Hadamard matrix, the first column of the Hadamard matrix is all 1 or all −1. As compared with the existing Rel-10 codebook, the codebooks designed according to the invention can reduce a feedback overhead and improve the average spectrum efficiency of a cell and spectrum efficiency of a user at the edge of the cell.