Using full-muffin-tin-orbital molecular-dynamics method, the electronic and geometric structures of GanAsn (n=4,5,6) ion clusters and their stability have been investigated in detail. The lowest energy structures are found. Our calculations suggest that they are obviously different from the ground state structures of their corresponding neutral clusters. In addition, the stable ionic structures have more severe structural distortion than the neutral structures. Gallium atoms occupy the cap atom positions more easily than arsenic atoms in the mixed GanAsn clusters.