It is known that choosing the appropriate MIMO modes in varied situations can achieve better transmission effects. We investigated the switch technology of the MIMO modes in TDD LTE downlink for the purpose of reaching the best average throughput as well as spectrum efficiency, and of enhancing the system’s transmission rate. The PDSCH simulation platform of TDD LTE downlink control channel is built to simulate the MIMO transmission modes. By comparing the simulated results in different modes the switch threshold is determined and an adaptive algorithm of switching MIMO modes is proposed, which render the user optimal the transmission efficiency in different situations.