To solve the bottlenecks associated with traditional Synthetic Aperture Radar (SAR) systems related to the limitations of single working models and core indexes, a new system known as Multi-Input Multi-Output (MIMO) SAR was recently proposed. This novel radar system obtains greater freedom by the use of more equivalent transceivers. As such, it is not constrained by the limitations of traditional SAR systems and can achieve high-resolution wide-swath imaging and mean-time multi-mode operation. In this paper, we analyze the connotations and characteristics of MIMO-SAR in depth, and summarize the current research situation and future development trends. To lay a foundation for China’s future SAR technology, we have also developed the first MIMO-SAR prototype with the same time-frequency coverage. We summarize the key technologies and flight results and analyze the prospects for MIMO-SAR applications.