Abstract: Using infrared scanning system principle, a novel long-wavelength continuous zoom scanning optical system is presented based on 4×288 infrared MCT detector dewar cooled assembly. Related optical index parameters are resolved and calculated according to requirements of system, and the optical design parameters and outside view are obtained by the optical design software. The narcissus effect of the scanning optical system are analyzed and optimized. The optical system is composed of zoom telescope, scanning mirror, relay lens, imaging lens and a tertiary imaging system including nine lenses and two reflectors. In order to reduce cost and optical color aberrations, chalcogenide glass lens is used. The optical index is simulated, and the MTF in whole field at Nyquist frequency is over 0.35 and distortion is below 2%.Finally the system imaging experimental verification is conducted. The results indicate that 30.8~154 mm continuous zoom and 100% cold shield efficiency are achieved. High resolution, thermal sensibility, excellent images are validated.