The image fusion technique is applied to the field of Terahertz (THz) image processing to solve the problem that THz cameras offered low-resolution images , which do not match the human visual habits. A fusion algorithm is proposed based on region segmentation and Nonsubsampled Contourlet (NSCT). The THz image is divided into target area and background area ,which are mapped into the visible images in next step, and the different rules are designed in NSCT domain. Experimental results show that the proposed algorithm displays the target, retains the background and detail information effectively. This algorithm is more feasible than traditional fusion algorithm based on pixel and regional energy in the human eye perceives, and can be used effectively for machine vision and terahertz security area.