The invention provides a precoding-scheme-based downlink precoding method for a multi-user multi-input and multi-output system. The precoding-scheme-based downlink precoding method comprises the following steps: a base station determines an original channel matrix according to information fed back by all users; user scheduling matrices of which the number is equal to that of the users are determined; antenna scheduling matrices of which the number is equal to that of receiving antennas are determined for all the users; each user randomly selects an own antenna scheduling matrix to replace an element, of which the value in a corresponding column is 1, in the user scheduling matrix so as to obtain K sending matrices; the original channel matrices respectively premultiply the K sending matrices to obtain K equivalent channel matrices; the K equivalent channel matrices are subjected to orthogonalization transformation; the reciprocals of the main diagonal elements of all judgment matrices are subjected to square operation and then summation; the optimal feedback matrix, the optimal weighting matrix and the optimal feedforward matrix are subjected to THP precoding. According to the precoding-scheme-based downlink precoding method, the original channel matrices are optimized, so that co-channel interference among the users is effectively eliminated.