The method of B3LYP/6-311G(d) in density functional theory(DET)was used to optimize the geometric configuration and study the photoelectron energy spectrum of Ga2Asn (n=1-5) ion clusters. The ground-state structure of the clusters has been obtained, the stability of which shows a certain degree of even/odd alternation with the increase of the total atoms number. The structure with odd number of total atoms is more stable than those with even number of total atoms in Ga2As-n clusters, while it is quite the contrary in Ga2As+n clusters. The energy gap between the highest-occupied molecular orbital (HOMO) and the lowest-unoccupied molecular orbital (LUMO) displays a certain degree of even/odd alternation, with the increase of the arsenic atoms number. The energy gap values with even number of arsenic atoms are basically the same, but they are rather different with odd number of arsenic atoms.