A novel modified optimization technique known as the multi-objective micro particle swarm optimization (MO-MicPSO) is proposed for polyphase coded signal design. The proposed MO-MicPSO requires only a small population size compared with the standard particle swarm optimization that uses a larger population size. This new method is guided by an elite archive to finish the multi-objective optimization. The orthogonal polyphase coded signal (OPCS) can fundamentally improve the multiple input multiple output (MIMO) radar system performance, with which the radar system has high resolution and abundant signal channels.Simulation results on the polyphase coded signal design show that the MO-MicPSO can perform quite well for this high-dimensional multi-objective optimized problem. Compared with particle swarm optimization or genetic algorithm, the proposed MO-MicPSO has a better optimized efficiency and less time consumption.