In terahertz imaging, the sparse design of the array can cause degradation of the grating-lobes. In this paper, based on the traditional coherence factor(CF) weighting method, phase coherence factor(PCF) and sign coherence factor(SCF) are designed, which are applied to multi-input and multi-output(MIMO) terahertz sparse array imaging grating-lobes suppression. The simulation results of the point target show that the peak side lobe ratio(PSLR) is reduced by 17.81 dB, 24.56 dB and 22.74 dB after grating lobes suppressed by CF, PCF and SCF, respectively. The results measured in the 340 GHz 4T16R sparse array imaging system also show that the suppression effect of PCF and SCF on grating lobes is 6dB and 4dB better than CF, respectively.