A summary of a 0.34 THz standoff 3D imaging radar is presented which can be used for through-clothes imaging of person-borne concealed objects. Using a two dimensional non-uniform point-by-point scanning mode, a field of view of 0.6 m×1 m and 2 s imaging speed is achieved. The central frequency is 0.34 THz, and a 2 cm azimuth resolution at 5.8 m is obtained by using a ellipsoid with a diameter of 450 mm. In order to improve the dynamic range of the system, a phase noise cancellation structure is adopted. The Frequency-Modulated Continuous-Wave(FMCW) radar technique with a 12 GHz bandwidth is employed in the system. Imaging result shows that 2 cm range resolution can be achieved after calibration and the system can be utilized to detect concealed weapons.