Mueller-matrix elements of hexagonal ice crystals in random orientation are calculated by the discrete dipole approximation (DDA) method and the profiles of Mueller-matrix elements are presented.The influence of the aspect ratio on Mueller matrices of hexagonal ice crystals in cirrus cloud is discussed. The results show that the influence of the aspect ratio on Mueller matrix elements of hexagonal ice crystals in random orientation is quite large in certain angular regions,and it varies with the size parameters of the hexagonal ice crystals in random orientation. In addition,there is a nodical point in the profiles of mueller matrices of hexagonal ice crystals with the same sizes but different aspect ratios,and this point will extend forward with the increase of the size parameters of particles.