Under the background of safety inspection, the key technologies of near-range passive millimeter wave focal plane array imaging are studied. The analysis of the system quasi-optics were carried out using fundamental Gaussian beam method combined with geometrical optics method. A multi-beam wide-angle scanning lens antenna was designed. A new dielectric rod antenna was devised, which is prone to be aligned in close arrays and provide good radiation to the lens. Miniaturized direct-detection radiometers were fabricated with high-sensitive in Ka-band . Experimental results of the 20-channel passive millimeter wave focal plane array imaging system are presented, which can be used to detect hidden objects on human bodies in near range indoors.