Most aerospace optical instruments are expected to perform over a wide temperature range. The change in temperature will cause not only the change of the curvature of optical elements as well as the refractive index, but also the change of the defocus of the image surface and therefore the degradation of performance. Based on adopted optical compensation method and with 1 920×1 080 visible high-definition CCD, an athermalized optical system working at-40 ℃～+80 ℃ is designed. The focal length of optical system is 12 mm, the F number is 4, and the field of view is 57.5. The results show that the system has a good imaging quality and the modulation transfer function (MTF) for spatial frequency is closed to the diffraction limitation over the temperature range.