Abstract: The orthogonal performance of the transmitted waveforms directly determines the capability of MIMO radar system. An ideal quasi-orthogonal waveform is orthogonal discrete frequency coding waveform (ODFCW). The ambiguity function of orthogonal discrete frequency coding waveforms was analyzed firstly and the theory suggested that the performance of ODFCW has related with the code length and coding order. In this paper, we used the cross-correlation energy as the cost function and applied the improved discrete particle swarm optimization (IDPSO) to design ODFCW. The proposed quasi-orthogonal ODFCW can be used in wideband MIMO radar and simulation results validate the effectiveness of the new algorithm, and with the increase in code length and the optimization of coding order, the cross-correlation level becomes lower, and Doppler tolerance is inversely proportional to code length. However, due to the inherent characteristics of ODFCW, its autocorrelation has almost no relationship with the code length.