Abstract: The influence of the aspect ratio on the scattering properties of small size hexagonal ice crystals in cirrus cloud is studied by using the discrete dipole approximation (DDA) method. The scattering properties such as phase function, extinction efficiency, asymmetrical parameter, single-scattering albedo and degree of linear polarization are computed. The results show that the influence of the aspect ratio on the scattering properties of randomly oriented hexagonal ice crystals is significant, and it varies with the size of the particles, but it is independent of the incident wavelength. In addition, there is an intersection point in the profiles of phase function of hexagonal ice crystals with the same sizes but different aspect ratios, and this point will extend forward with the increase of particle size. The result provides a theoretical basis for the object acquisition and identification.