Terahertz (THz) technology is increasingly being used in a wide range of applications, and terahertz radar systems have also been developed in radar applications. In this paper, the terahertz radar system is used for 2 dimensional (2D) realtime imaging in near-field scenario within 20m. A real-time imaging system of 170GHz Synthetic Aperture Radar (SAR) is designed, and the system is simulated and verified by Doppler Beam Sharpening (DBS) algorithm. The simulation results show that the system can utilize uniform linear motion to synthesize a short aperture in the near-field range and form 2D image of scattering points in the scene. The imaging effect is good.