Terahertz coded-aperture imaging is a novel imaging technique which follows the basic principles of optical coded-aperture imaging and microwave coincidence imaging. It is based on the modulation of the effective terahertz-wave spatial distribution, either amplitude or phase, over the illuminated area. The wave spatial distribution or illumination pattern is usually obtained by a reflecting antenna. Terahertz coded-aperture imaging has some significant advantages such as high frame rate, high resolution, and the ability of forward looking and staring imaging. Hence it has been regarded as one of the most important development trends of terahertz radars. In this paper, we at first introduce the proposition background of this new technique, and then expound its principles, research states of the art, an implementable setup and the key problems. Finally, the application fields including missile terminal seeking and security as well as anti-terrorism are discussed. We hope that this paper can provide some positive guidance for the study of terahertz coded-aperture imaging and the corresponding new terahertz radar.