A powerful HARQ-based linear precoding scheme is proposed to utilize the flexibility of post-combining HARQ strategy in MIMO communications systems. The scheme selects the appropriate symbols and transmit powers for each eigen-mode to acquire more performance gains. Simulation results show that the proposed scheme achieves about 5.5 dB signal-to-noise ratio gains over original spatial multiplexing scheme at an average bit error rate of 10-4. Furthermore, the gap between the two schemes increases with the number of transmissions.