A compact thermal imaging system, operating over both near and far distances, for armed police is introduced. A design example is proposed. The working band is 8–12 .m, the center wavelength is 10 .m, the long focal length is 150 mm, the short focal length is 50 mm, and the F number is 1.1. The system can match the performance of an uncooled focal plane infrared detector with a pixel number of 384.288 and a pixel size of 17 .m.17 .m. The system realizes zooming by the axial movement of the zoom group. By using binary optical surface and aspheric surface, the volume and mass of the imaging system are reduced, and the image quality is improved. The design results show that the thermal imaging system has appropriate image quality, which is suitable for fire rescue, fire prevention, night detection, and border monitoring.