A summary of the CAS EMRST key laboratorys three-dimensional(3D)imaging radar is presented,with the emphasis on several key aspects that enable fast personal screening for concealed objects detection.Based on the combination of real aperture and synthesized aperture focusing with fast fan-beam scanning,sub-centimeter resolutions are achieved in the cross range directions.The approaches of the reversed ray tracing algorithm(RRTA)and a modified physical optics method were incorporated to design and optimize the beam scanning quasi-optics with 2.5 dimensional electrically ultra-large structures.Using FMCW transceiver developed in THz band with high frequency modulating rate and broad bandwidth,the target distribution in range direction can also be recovered with high resolution.Special image reconstruction algorithm with high efficiency is developed for the system and accelerated by parallel processing techniques to achieve the real time capability.This work makes pioneering and comprehensive explorations to develop synthesized aperture technology in THz band.The real time system developed is practical for stand-off security surveillance with high 3D image quality.