The athermalization method for dual-wavelength infrared optical system is introduced. An athermalized dual-wavelength infrared dual-view optical system is designed. The optical system adopts the passive optical athermalization technology and a re-imaging system. A passive optical athermalization design of dual-wavelength infrared optical system is presented by using three common materials Ge, ZnS and ZnSe and two aspherical surfaces. The results show that the optical system working in the 3.7～4.8 μm and 7.7～10.3 μm wavelength bands has a compact structure and can meet the requirement of 100% cold shield efficiency. The imaging performance of dual-wavelength infrared optical system is very well in the temperature range from -60 ℃ to 70 ℃. The correctness and feasibility of the design method are proved.