The single scattering properties of the hexagonal ice crystals with a gamma particle size distribution were calculated by using the ray-optical theory at some wavelengths located in the visible and infrared spectral region(0.2-5 μm).The single scattering properties of the sphere particles having equal surface area with hexagonal ice crystals are calculated with Mie theory.Based on radiative transfer theory,the reflection properties of cirrostratus consisting of hexagonal ice crystals or equivalent spheres are computed by using the adding-doubling method,respectively.The results show that the Mie scattering calculations at the region of λ≈3.0 μm give good agreement with the hexagonal ice crystals.However,there are large errors at the region of λ<2.8 μm,especially,at the visible region.Finally,the schemes for calculations of the optical properties of ice clouds are proposed.