Terahertz (THz) waves have great application potential because of their unique atmosphere sensitivity features and spatial transmission properties. This study summarizes the research achievements of major research institutions at home and abroad in THz space exploration. Further, we describe the parameters, working environment, and detection results of large ground-, aircraft-, and space-based THz space exploration platforms and compare the experimental results of these platforms. In addition, the features of THz remote sensing equipment are also analyzed. Finally, we present the application prospect and future development trends of THz space exploration. The THz space exploration technique can obtain unique information that cannot be acquired using optical methods or microwave technology, which makes it a prospective research area in the future. The development of THz space exploration technology will lay an important foundation for high-resolution space remote sensing.