Abstract: Resolution, imaging time and distance are crucial parameters for terahertz imaging technology. In order to improve the terahertz imaging capability for practical use, especially for quick identification and alarm for hidden objects in a long distance, a passive rapid terahertz scanning imaging system for long distance was presented. In terms of core scanning system,a hexahedral mirror for twodimensional fast scanning through high speed rotating and reciprocating swing combination was employed. The system was placed in the parallel light path of the offaxis threemirror system. The scan area focused on image space instead of the object space, which could effectively narrow the scan area, so as to shorten the imaging time. The main parameters of the passive scanning imaging system are as follows: the detector frequency is 0.34 THz, the imaging distance is 10 m, the field of view is 1.51.5, the resolution is 3 cm, and the imaging time is 1 s.