The reflectance of cirrus atmosphere from 0.4 μm to 2.5 μm is simulated by a combined atmospheric radiative transfer (CART) software. The effects of wavelength, optical thickness, effective size, cirrus altitude and surface type on the reflectance of cirrus atmosphere are analyzed. The relationships between reflectance of cirrus atmosphere at 0.55, 1.38 and 2.75 μm bands are simulated. Results show that the reflectance increases with optical thickness from visible with near infrared wavelength regions. Variation of the reflectance with effective size of cirrus clouds is small at the visible band, and the reflectance decreases with effective size at near IR wavelength band. The reflectance increases with cirrus altitude at IR absorption band of water vapor. Variation of the reflectance with different surface types is distinct in the atmospheric window region. The cirrus optical thickness and effective size can be retrieved with the relationship between reflectance of cirrus atmosphere at 0.55 μm and 2.75 μm, 1.38 μm and 2.75 μm bands.