We present here an in-depth study upon the interaction between a neutral cluster Al13 and a typical ligand tetrahydrofuran (THF) via density functional theory (DFT) calculation. It is found that electron delocalization over the framework of Al13 and THF facilitates ligand-to-Al13 charge transfer leading to enhanced stability for the superhalogen cluster Al13. Further study on the stabilization of Al13(THF)n cluster complexes with n = 1-8 reveals that the adsorption of more THF ligands gradually enhances the total binding energy and the total electronic charge transfer from the ligand to Al13. The bonding nature and stabilization of Al13(THF)n cluster are then demonstrated by rationalizing the interactions between superatomic and molecular orbitals of Al13 and THF, respectively.