A passive terahertz imaging system with high resolution and long distance is designed by using the terahertz wave imaging method. The system consists of a scanning module, terahertz detectors and quasi-optics. The system has the operating frequency of 110 GHz, the object distance of 6.0 m, and the detector field of 2.0 m×0.8 m. The resolution of the system is 2.5 cm. It is simulated and verified by experiments in GRASP. This system can check the articles carried with human body at a no-touch and non-stop way.