First-principles calculation is used to study the hydrogen molecule adsorbed on Ti-doped Al(110) surface and pure Al(110) surface separately. We find an adsorption path of hydrogen molecule for decomposing hydrogen atoms and forming TiH2 with Ti atoms on top site. Afterwards, the TiH2 molecule moves to hollow site and approaches to the Al(110) surface. The analyses of density of state and Milliken overlap population show that there is covalence interaction between hydrogen atoms and Al atoms of surface, which gives rise to the formation of Al-H, Na3AlH6 and NaAlH4. Hydrogen molecule is unable to decompose hydrogen atoms on pure Al(110) surface.These results contribute further towards the understanding of the improved observation in recycling of hydrogen with Ti-doped NaAlH4.