The present invention provides a method and system for transmitting Multiple Input Multiple Output (MIMO) beam forming data. The method comprises: performing MIMO coding on data streams to obtain the coded data streams; obtaining weight values W=(Wi,j)Tx×S for beam forming of an antenna array of Tx×S of a transmitting end based on channel information from the antenna array of the transmitting end to antennas of a receiving end, where Tx is the number of transmitting antennas of the transmitting end, S is the number of the MIMO-coded data streams, and S≦Tx; and weighting the coded data streams with the weight values W=(Wi,j)Tx×S for beam forming, and transmitting the weighted data streams by corresponding antennas, where the data transmitted by antenna i is superposed data ∑ j = 1 S ⁢ W i , j ⁢ x j , i = 1 , … ⁢ , Tx , j = 1 , … ⁢ , S , and xj is jth coded data stream.