THz Array imaging has wide application foreground because of the high imaging speed and large detection area. The design of optical path has great effect on image quality. The THz real imaging system is constructed by use of the SIFIR-50 THz laser as imaging illuminant and Pyrocam Ⅲ thermal imager as array detector. The system has been improved using a series of off-axis parabolic reflectors and polyethylene lens. Imaging experiments on the object of water mark, hollowed-out metal board and resolution board have been made and clear images are obtained. By comparing with original imaging results, it is validated that the imaging quality is well improved. By analyzing the imaging results, resolution of the imaging system can be evaluated and reaches up to 0.6 mm.