There is provided a down link multi-user time-space code precoding method including: a step (S401) where a base station acquires channel information on a plurality of user terminals and converts it into a channel matrix; a step (S402) for obtaining a such a conversion matrix that a matrix obtained by multiplying the channel matrix and the conversion matrix is a block diagonal orthogonal matrix; a step (S403) for obtaining a standardization factor of each user terminal by squaring the elements on the diagonal line of the block diagonal orthogonal matrix; a step (S404) for standardizing a transmitted symbol of each user by using the standardization factor; and a step (S405) for multiplying the conjugate transposed matrix and the conversion matrix of the block diagonal orthogonal matrix into standardized symbols successively from the left so as to obtain symbols after the processing and transmitting the processed symbols by the time-space code rule. This method improves the downlink performance and effectively improves the radio system capacity.