An apparatus and method for transmitting in a multi-user multi-antenna system are provided. The apparatus includes a precoder for orthogonalizing a channel by removing a channel element of a corresponding terminal with respect to multiple terminals, for determining an effective channel of each terminal by decomposing the orthogonalized channel using Singular Value Decomposition (SVD), for determining a precoding matrix using the effective channel, and for mapping data streams of the multiple terminals to a plurality of transmit antennas using the precoding matrix, and the plurality of the transmit antennas for transmitting the data streams of the multiple terminals. Hence, it is possible to obtain an iteration algorithm performance requiring considerable computation while avoiding complexity and reducing computation.