Abstract: Low-level-light color night vision systems are developing from the single band to the multi-band, and information from visible band and long wave infrared (LWIR) band is used to generate fused image and color vision. A dualband optical system is developed, which made of Ritchie-Crtien(R-C) system, correcting lens, and the beam-splitter which reflects in visible region and transmits in the long wave infrared(LWIR) region. Its full field of view and relative aperture are 50 and F/1.7 respectively, the ratio of scondary mirrors central obstruction is 1∶3, and MTF is higher than 0.60 at 50lp/mm in the visible region, higher than 0.30 at 18lp/mm in the LWIR region. The features of the lens are discussed. The aberration curves and MTF curves of the system are presented.