Al2-Al40 clusters were studied by means of the all-electron DFT method.The properties of the aluminum clusters including binding energy,the second difference in energy,HOMO-LUMO gap,especially fragmentation energies and ionization potentials,were analyzed.The main products from the dissociations of aluminum cluster ions are shown to be Al+Al+n-1 for the larger clusters,and Al++Aln-1 for the smaller ones.And,the calculated ionization potentials are consistent with the experiment data. Al2-Al40 clusters were studied by means of the all-electron DFT method. The properties of the aluminum clusters include binding energy, the second difference in energy, HOMO-LUMO gap, especially fragmentation energies and ionization potentials, were analyzed. The main products from the dissociations of aluminum cluster ions are shown to be Al + Al + n-1 for the larger clusters, and Al ++ Aln-1 for the smaller ones. And, the calculated ionization potentials are consistent with the experiment data.