In order to solve the technical problems that the refraction optical system is not easy to achieve the long focal length miniaturization design and the reflection optical system is not easy to achieve the large field of view, the shortwave infrared imaging optical system with the focal length of 500 mm, the operating band of 09－17 m and F number of 5 is designed by using an optical structure with the form of refraction and reflection. The system consists of a parabolic primary mirror, a quadric secondary mirror and a rear set of lenses, with a total optical length of 138 mm. The design results show that the system has a compact structure, small size and good imaging quality. The value of modulation transfer function (MTF) at the characteristic frequency of 33 1p/mm corresponding to the detector is greater than 055, which is close to the diffraction limit. MTF test and location imaging test are carried out after the assembly of the whole machine. The actual test results are consistent with the design analysis and meet the application requirements.