Abstract: To analyze the effect of stray light on infrared imaging system comprehensively, a common aperture imaging optical system was designed for both visible band(0.4 μm~0.7 μm) and infrared band(3 μm~5 μm) while the field of view is 2.27°×2.27°. By analyzing the stray light source, the effect of in-band stray light and off-band stray light on imaging quality of infrared channel was studied respectively. The structure of the hybrid light was designed for in-band stray light and the suppression capability was simulated and analyzed by FRED optical software. According to the result, the in-band stray light can be suppressed well, the ghost impact is negligible, and the point sources transmittance (PST) of solar stray light suppression level reaches the set threshold level of 10^-8. For off-band stray light, the influence of 1.064 μm and 2.6 μm infrared laser on infrared imaging system was mainly studied by finite element method. Results show that the in-band infrared radiation can be generated strong when the temperature of system mirror rises to 703 K and the radiation power to the image plane reaches 0.069 mW, which can cause strong noise interference on the infrared imaging surface.