The study of terahertz radar scattering characteristics is important for target identification, tracking, and interception. A 0.22 THz stepped-frequency Radar Cross Section (RCS) measurement system is designed, and the RCS extraction method is also proposed. Using the combination of experiments and simulations, the terahertz radar cross section of a single corner reflector and corner reflector group within 4° is obtained. The results show that the RCS experimental results and the theoretical calculation results of the corner reflector target are in good agreement within the error range, which lays the foundation for further accurate measurement of the scattering characteristics of the target in the THz band.