We present here a further insight on the hydrogen evolution reactions (HER) of aluminum clusters with one and multiple water molecules. Along with natural bond orbital (NBO) and frontier molecular orbital (FMO) analysis, we compared the reactivities of both anionic and neutral Al-13, Al-12, Al-7, and Al-6 clusters with water in gas phase. It is found that electron flow interactions between these typical Al clusters and H2O initiate their reactions, allowing varied charge distribution on the cluster. With an emphasis on the typical Al-6 cluster, we checked out the reactive intermediates, activated complexes, transition states, bond breaking and stereochemistry for it to react with two and four water molecules, respectively. The kinetic-and thermodynamic-allowed reaction pathways are coincident with the experimental observation of Al-n(OH)(4) being dominant products for Al-n(-) clusters reacting with water. It is illustrated how additional water molecules function as catalysts enabling strengthened HER activity.