Abstract: Multiinput multioutput synthetic aperture radar (MIMOSAR), a new kind of radar regime, could obtain more equivalent observation channels than the number of the physical antennas by utilizing multiple transmitting and receiving antennas. Compare with traditional SAR regime, MIMOSAR has significant potential on highresolution wideswath remote sensing, detection of slowly moving targets and three dimensional imaging, etc. An overview of the overseas and domestic research status on MIMOSAR waveform design and high resolution imaging techniques is presented in this paper. Key technologies including optimal orthogonal waveform design, azimuth imaging without ambiguity and enhancing range resolution, are discussed. Finally, some key issues to enhance the imaging performance of MIMOSAR are introduced which deserve more attention in the future.