Abstract: The mode switching is investigated for MIMO systems with considering four practical factors including channel estimation error, packet loss probability constraint, Automatic Repeat reQuest (ARQ) technique, discrete transmission rate and practical codec performance. The closed-form expressions of throughput are derived for spatial multiplexing and diversity modes, based on which the adaptive throughput-based mode switching is proposed. Numerical results show that the proposed scheme outperforms the fixed transmission mode schemes and the considered factors affect the throughput and the mode switching point.