Structures and stability of GanN-(n=2—8) and GanN-2 (n=1—7) anionic clusters have been studied using the density functional theory (DFT). Structural optimization and frequency analysis were carried out at the B3LYP/6-31G* level. All ground states of GanN-(n=2—8) and GanN-2 (n=1—7) clusters have been obtained. Our calculations reveal that there exists a transition from planar to spacial structures at the total number of the atoms being 5 with increasing cluster size. Among different GanN-(n=2—8) and GanN-2 (n=1—7) anionic clusters, Ga4N-， Ga6N-, Ga4N-2 and Ga5N-2 are more stable.