Dualcolor infrared optical systems can obtain LWIR and MWIR information simultaneously, which would be good for the target tracking and recognition. As to the needs of the infrared thermography, dual FOV /dual color infrared optical system is designed with simplified optical configuration. Dual color (4.4~5.4 μm/7.8~8.8 μm) clear imaging is achieved, and double view switch (9°×6.75°/3°×2.25°) can be completed by switching variable group when F# is constant(2.68). Through rational distributions of IR material and focal power, the optical passive athermal design achieves. The results indicate that when the systems works on －40℃~60℃,the image plane is stable and the image quality is excellent, which can meet the using requirement of infrared thermographs.