Abstract: Using the terahertz imaging technology for its microwave penetration characteristics and high resolution of infrared imaging, a near-field terahertz passive synthetic aperture imaging system is put forward on the basis of the infrared and millimeter wave imaging system. Its realization method is briefly analyzed as follows: a 2-D beam scanning antenna structure is used to realize antenna aperture synthesis, through scanning the two antenna beams to acquire the visibility function, then the terahertz image can be obtained by relevant imaging algorithm; this structure can reduce the complexity of the system and guarantee the imaging system performance at the same time. The performance of this system is analyzed by numerical simulation, and the simulation results show that the system has high spatial resolution. Finally, the feasibility of the imaging system is verified by the process simulation of synthetic aperture imaging.