The distribution of forward small-angle scattering radiation is related to the particle size and optical thickness of the scattering medium. The forward small-angle scattering ratio, atmospheric optical thickness τ and the Angstrom index α of aerosol particles are measured based on a new type of variable field photometer under different weather conditions. The results are compared with the results of DISORT simulation. It is shown that the scattering ratio increases with increasing of optical thickness. However, when the optical thickness is less than 1, the scattering ratio would depend on the effective scale of the particle. The larger the particle, the smaller the scattering ratio. When the size of cirrus ice crystal is larger (De>10 μm ), the scattering ratio is smaller than that of aerosol particles and water clouds. This provides a new method to distinguish thin cirrus clouds with aerosols. A simple method for extracting optical thickness of cirrus clouds is presented. It is proved that the extinction coefficient of cirrus clouds is independent of wavelength in short wavelength band. The research provides a certain reference for ground based detection on atmospheric properties.