Multiple-input and multiple-output (MIMO) wireless systems make use of multiple transmitted and received antennas to increase the communication system capacity through spatial multiplexing. Furthermore, combination of MIMO with orthogonal-frequency-division multiplexing (OFDM), which has simple implementation and robustness against frequency selective fading channel, has been widely used in many standards. Such as IEEE 802.11n, IEEE 802.20 and and J unqing Liu Abstr act An effective base expansion model (BEM) decomposition method for multi-input and multi-output (MIMO) channels is proposed. Channel parameter model is proposed to fit the time-varying space-frequency channel, which can be adopted to estimate the MIMO-OFDM channel state information. The result of channel matrix decomposition includes the main energy component and subordinate components, the subordinate components energy is decreasing with higher order decomposition. Two pilot styles are used to estimate the channel parameters; time-domain pilot block has low computational complexity. Simulations show that good performance can be obtained in MIMO space-time-frequency channels.