Abstract: The capacity of MIMO system is increased linearly with the number of the antennas in multi-path fading environments, and transmit/receive antenna selection barters little lost of system performance for great decreasing of RF cost, making MIMO system not fully limited by RF cost. To quickly select transmit/receiver antenna subset making the system capacity best, this paper proposes an adapted algorithm for the fast antenna selection algorithm, which reduces the computation complexity by updating the quantities in real time. Simulation results indicate that the algorithm decreases computation time a lot without any system capacity lost.