The B3LYP method of Density Functional Theory(DFT) is used to optimize geometry configuration of GanN3(n=1~8) clusters at the level of 6-31G*.The bond properties,photoelectron energy spectroscopy and stability are calculated and analyzed,and the most stable structures are obtained finally.The results show that there is a transition from planar to spacial structures at n=5 with increasing cluster size,and N-N bonds are more stable.The strong Ga-N bonds play an important role in GanN3(n=6~8).Among the GanN3(n=1~8) clusters,Ga4N3,Ga7N3 are more stable; Average polarizabilities are increased as the n value increases.The vibrational frequencies of Ga-N bond are close to the peaks of the phonon vibration modes of the wurtzite structure GaN by analyzed the photoelectron energy spectroscopy.