Abstract: A cooling-type mid-wave infrared broadband (2.7 to 5 μm) multi- spectral dual-field imaging optical system based on a filter and cooled detector is designed. A scene can be imaged by using an infrared-cooled detector through the corresponding filter. In this system, the filter wheel with multiple filters is placed in front of the detector to minimize the aperture of the filters and provide compatibility with non-uniformity correction functions. The filter wheel is rotated to obtain multiple required spectrum information, and the differential technology can better extract the target information and improve the sensitivity. The F-number of the system is 4, focal length is 70 mm/280 mm, and modulation transfer function is close to the diffraction limit. The system has an optical active athermalization function in the range of −50℃ to 80℃. The simulation results show that the performance of the system can meet the design requirement.