Orthogonal waveform separation is an important process to realize high resolution radar imaging for multi-input and multi-output synthetic aperture radar (MIMOSAR). In this paper, orthogonal frequency division multiplexing (OFDM) waveforms are used to realize the received echoes separation in one snapshot. Then, we reconstruct MIMO-SAR signal for each carrier frequency in multiple snapshots, and high range resolution is achieved by synthesizing the linear frequency modulation signals of different carrier frequencies at the same phase center of virtual element. Furthermore, cross correlation of OFDM waveforms and the integrated sidelobe rate influenced by the interval factor of center carrier frequency are analyzed in the range profile. Simulations demonstrate the validity of bandwidth synthesis method.