The spectral properties of sky background are discussed during the solar radiation transfer in clear atmosphere at 0.45～0.95μm. The results on the different solar zenith, different observational azimuth and given aerosol conditions are presented. All calculations are given based on Rayleigh scattering law,molecular absorption database, Mie scattering law and discrete-ordinate method(DOM). The theoretic analysis of spectral properties varied with aerosol kinds, wavelength, visual distance and observational azimuth is presented. By comparing with measurment, it is proved that the results accord with the actual observation data.