A high‐resolution imaging system for short‐range personnel security screening based on a novel multiple‐input‐multiple‐output (MIMO) array is presented. It overcomes the problem of specular reflection which occurs in the most state‐of‐the‐art mono‐static‐based configuration. Prior to the state‐of‐the‐art portal‐based architecture, this system is able to reconstruct three‐dimensional (3D) image of the whole body and detect a concealed weapon in secret while passenger walking through the hallway or intersection, which is a potential for realising a reconfigurable system to monitor the marching crowd. The architecture consists of four transmitter columns and two receiver circles, illumination area which covers the most concerned part of the human body. The reduced number of sensors and no moving part characteristic make authors’ system cost efficient and robust. A ray‐tracing technique is applied to fast estimate its illumination and imaging performance. Several numerical experiments based on the frequency modulated continuous wave model with 10–25 GHz frequency sweeping are proposed to reach both azimuth and range 1 cm resolution. 3D results of these experiments show that authors’ system works well on whole‐body imaging and threat object detection.