Abstract: In multiple-input-multiple-output (MIMO) orthogonal frequency-division multiple-access (OFDMA) systems the Least Square (LS), Linear Minimum Mean Square Error (LMMSE) and LMMSE Singular Value Decomposition (SVD) algorithms are commonly used in channel estimation. For this reason the paper addresses analysis and compare of these channel estimation algorithms based on complexity theory. In the paper, the channel platform is first supplied by MMO-OFDMA systems. Then these algorithms are simply introduced. Finally we have analyzed and compared time and space complexity of these channel algorithms and these results owned important reference value to the design of MIMO-OFDMA systems based on different channel environment.