regarding the poor work conditions of military infrared optical instruments, there is usually a strong demand for athermalization and high resolution design. according to the properties of diffractive components in the optical passive athermalization, a diffractive-refractive hybrid infrared optical system working at 8 um-12 um is designed. it only contains four lenses with two aspheric and two diffractive surfaces, resulting in solutions with reducing overall size and weight, as well as enhancing performance characteristics. the mtf of this system demonstrates the optical system can realize athermalization over the temperature range from -40 degrees c to 60 degrees c. in addition, the chromatic aberration and second spectrum are corrected simultaneously. (c) 2016 published by elsevier gmbh.