Terahertz time-domain spectroscopy technology has a wide range of applications in security inspection, nondestructive testing, biomedical, etc. But its application to target characteristics has been under debates, because there exist so many differences between terahertz continuous wave and ultra short pulse wave (single pulse width about 1 ps). For investigating the problem of quantitatively measuring the terahertz radar cross section, in this paper, a terahertz time domain spectroscopy scattering measurement system is built based on the technology of terahertz time domain spectroscopy. After system optimization and error minimization of location and system, time domain echoes of targets, such as sphere, disk, cylinder and complex targets, are measured. After the process of fast Fourier transformation and calibration, radar cross sections of the above-mentioned targets in a frequency range of 0.2–1.6 THz are calculated. Furthermore, the surface integral equation method and multilevel fast multipole algorithm are used to simulate the radar-cross section (RCS) results. The measured radar cross section results are compared with the simulations, and their error is less than 3 dB. The error arises mainly from the location and uneven distribution of terahertz wave on quiet zone. Generally, it is acceptable though there is still much work to do. The accuracy of RCS measurement of terahertz time domain is varified. All those are progressing in terahertz time domain spectroscopy technology used in target characteristics. Moreover, the methods of improving dynamic range in high frequency and enlarging quiet zone are the focus of follow-up studies.