The parameter changes of optical lens caused by temperature changes may result in defocusing of the optical system, and the purpose of athermalization design is to compensate for the influence of temperature changes, and match the detector with the image plane.Normal athermalization design methods mainly study the influence of temperature on refractive index, and the change of position, angle and surface of the optical elements due to structural deformation is not taken into full consideration.A detailed analysis is made to the influence of temperature on optical system in consideration of structural-thermal-optical effects.Then, an optical athermalization design method based on structural-thermal-optical integration simulation is studied, and the effectiveness of this method is verified by a passive athermalization design of Cassegrain optical system.