Using a first-principles pseudo-potential plane wave method, the geometrical and electronic structures of Aln (n=3, 4, 6, 13, 19) clusters with different configurations have been calculated. Several parameters such as the binding energy Eb and the HOMO-LUMO energy gap △EH-L have been adopted to characterize and analyze the structure stability of these clusters, and their configuration evolutions are also investigated by linear synchronous transit (LST) method. It is demonstrated that the stable configurations of Al3, Al4, Al6, Al13, Al19 clusters are triangle, rhombus, octahedron, icosahedron and double icosahedron, respectively. For Al6 and Al19 clusters there are metastable structures of parallelogram and octahedron, respectively, whereas in the Al3, Al4 and Al13 clusters, no metastable configuration is validated. There exist a large energy gap and a low energy barrier between the octahedron and the parallelogram of the Al6 cluster, so the transformation from its metastable to stable structures is rather easy. By contrast, a small energy gap and a high energy barrier between the stable and metastable structures of Al19 cluster mean its configuration evolution from the octahedron to the double icosahedron occurs hardly, therefore the metastable octahedron configuration of Al19 cluster can be extensively detected in experiments and simulations.