Abstract: Multi-carrier MIMO radar is a radar system with multiple transmitted antennas and multiple received antennas capitalizing on frequency diversity and spatial diversity to obtain orthogonality of transmitted signals and the methods based on the dechirp processing to obtain High Range Resolution (HRR) are studied in this paper. The IFFT coherent synthesis processing method and the excuse of spurious peaks are analyzed and then a novel signal processing method, Spatial Domain Synthetic Bandwidth (SDSB) approach, is proposed. The multiple carrier frequency LFM return signals transmitted spatially diversity are first deramped by the dechirp processing and then the individual channel signals after the channel separation are combined into an LFM signal with a larger bandwidth by time shift in sequence. Finally the IFFT processing is applied to the concatenated signal to achieve HRR. The approach can be implemented easily, can avoid the spurious peaks effectively without the addition of computation and has a slightly influence on the moving target. Finally the simulation results on the computer validate these conclusions.