Infrared radiance characteristic of cirrus atmosphere is the main clutter sources for advanced space-based electro-optical detecting systems. Based on bulk scattering parameters of cirrus particles in 2.7 μm and 4.3 μm wavebands, cirrus atmosphere radiance transfer model was constructed. With cirrus and atmosphere parameters measured by MODIS, the infrared radiation images of cirrus atmosphere were calculated. The statistical results of all pixels show that, in the 2.7 μm band, the average radiance is 1.832e-2±3.024e-2 W/(m2·sr), and the average radiance of cirrus pixels is 433 times larger than that of the clear-sky pixels; For 4.3 μm in-band radiance of all pixels, the average value is 3.027e-2±2.99e-3 W/(m2·sr), the maximum value is 2.37 times as large as the minimum.