At present, the mechanism and devices of terahertz radar detection and imaging has attracted a lot of interest. Based on 4-f terahertz time-domain spectroscopy (THz-TDS) technology, a broad-band time domain terahertz radar system (0.1- 1.3 THz) was built for scattering and imaging characteristics of objects. Far-field radar cross-section measurements of different metal scaled models at terahertz frequencies were performed. The novel broadband radar can provide RCS distributions at arbitrary frequency and frequency-averaged RCS. Moreover, based on improved filtered back projection algorithm, imaging of the scaled models has also been retrieved, which can be helpful for scattering points searching and military shape optimization.