For the low background detecting infrared opto-mechanical systems, the signal is very weak and the spontaneous emission of the system has a large impact. This paper discusses the optimized design of infrared opto-mechanical systems based on the spontaneous emission suppression. The refraction-reflection system, coaxial reflection system and off-axis reflection system are compared on the spontaneous emission suppression in the way of effective emissivity and equivalent blackbody radiation temperature(EBRT). We find that the reflection system is better than refraction-reflection system and the off-axis reflection system is the best. From the change of equivalent blackbody radiation temperature, the paper introduces choosing the wavelength range, the optimized design of opto-mechanical structure and the surface processing. It is concluded that the even longer wavelength detecting has clearly advantage in the low background and it is better that the reflective surfaces and black surfaces has reasonable layout. The impact of refrigeration to the opto-mechanical systems suppressing the spontaneous emission is discussed. We find that refrigeration system can suppress spontaneous emission obviously, while the efficiency is worse when the refrigeration temperature is lower. So the crucial surfaces refrigeration can be adopted.