Reducing the correlation level lies at the core of the waveform design for multiple-input multiple-output (MIMO) radar system. In this paper, a new approach to the design of waveform for MIMO radar is proposed. The multiple pulse train coding is employed and the compression accumulation is introduced. In this manner, the waveform correlation can be almost eliminated and the optimal compression accumulation results with low range sidelobe is obtained. Numerical simulations demonstrate that the performance of the proposed approach is superior to that of previous state-of-the-art algorithms.