Abstract: With the purpose for simultaneously capturing infrared pictures and spectral information of an object, a four-channel aperture-divided and multispectral optical imaging system was designed and analyzed. Relying on the approach of separating the aperture and placing the appropriate filter in individual channel, the object with four infrared bands can be imaged on the corresponding regions of the cooled infrared detector. Four infrared bands include 3.5 μm~4.1 μm, 4.4 μm~5 μm, 3.5 μm~5 μm as well as 4.4 μm, respectively. The F-number of the system is 1.93, and the focal length of the single channel is 60mm.Moreover, the modulation transfer function (MTF) is close to the diffraction limit.In particularly, our system satisfies the demanding of athermalization in the range of -40 ~+60℃. The simulation results show that the performances of the system can meet the requirement of design.