Abstract: The problem about waveform design in multiple-input multiple-output (MIMO)skywave radars is analyzed in detail inthis paper, aimed at the requirements of skywave radar operation in practice. With the analyses, the advantages, disadvantages,suited primary mission and some other respects of several typical waveforms are compared, and the relationship of part of the waveforms is got. To improve the shortcoming of the waveforms at Doppler tolerance, speed ambiguity and frequency restrict, a set ofslow time random phase-coded(STRPC) waveforms is proposed. The conclusions of analyses and comparison and the improvementin waveform design supply reference to the signal theory study and practical realization in MIMO skywave radars.