The performance of the optical system is susceptible to changes in operating temperature,so thermal analysis and athermal design are required when designing the optical system.The influence of operating temperature on the performance of the optical system is studied,the thermal analysis parameters of optical components are introduced,and the relationship between the structural parameters of the optical system and temperature variation is discussed.Then the shortcomings of the Code V in the thermal analysis function are pointed out.After studying the principle of thermal analysis,the two aspects of the calculation of the optical element interval and the calculation of the refractive index of the optical material are improved by writing a macro file,and finally an athermal optical system working at -20～85℃ is designed by Code V.The focus length of the lens is 2.8mm,F number is 2.2,and the field of view is 160°.The design result shows that the imaging quality is good in the entire operating temperature range and meets the requirements.