The English abstract. Near-field passive millimeter wave imaging is one of the most promising technology for the safety inspection of concealed weapons. A quasi-optical system of near-field millimeter wave imaging is designed based on geometrical optics and Gaussian beam method. The system uses a pair of planar mirrors to scan the target plane along vertical and horizontal directions, respectively. A double refraction lens is used to realize focus imaging of millimeter wave. The bolometer working at 3 mm wavelength is used as a detector to receive millimeter wave radiations. The distance between the target plane and the system is less than 1.5 m, the imaging area is 1.2 m×0.6 m and the spatial resolution is 30 mm. The theoretical analysis and simulation results prove that the system has good imaging quality and meets the design index. The system can be applied to the public inspection fields and realize non-contact safety inspection, which will adapt to the development of near-field passive millimeter wave imaging system with light weight, compact volume and high imaging quality.