We present a mathematical model of radiative transfer through the atmospheric clouds with optical anisotropy with respect to zenith angle of incident radiation. An algorithm of statistical modeling has been developed to simulate solar radiative transfer through anisotropic scattering medium taking into account multiple scattering. We present the results of numerical experiment for media comprising ice crystals having the shape of hexagonal cylinders of different orientation in space. The local optical characteristics of anisotropic medium (scattering phase functions and scattering cross sections) were calculated based on the geometric optics approach. We have compared the radiative properties of clouds for crystals isotropically orientated in a horizontal plane and in space. Possible influence of crystal orientation on albedo of the cloud layer and the shape of halo is demonstrated.