Three-Dimensional (3D) Synthetic Aperture Radar (SAR) imaging has considerable application potential in steep-terrain mapping and target recognition in complex environments and is an important development direction in the current SAR field. To promote the development and application of the 3D SAR imaging technology, the Aerospace Information Research Institute, Chinese Academy of Sciences designed and developed an unmanned aerial vehicle-borne Microwave-Vision 3D SAR (MV3DSAR) experimental system, which provides an experimental platform for the research and verification of related technologies. Currently, the single-polarization version of the system has been developed, and the first flight experiment has been conducted in Tianjin. This study introduces the structure, performance, key technologies, and data processing of the system. This study also presents the implementation and preliminary data processing results of the first experiment, verifying the basic performance and 3D imaging capability of the system. The MV3DSAR provides a good experimental and verification platform for analyzing 3D SAR imaging algorithms and constructing 3D SAR imaging datasets.