We study the effect of oxygen vacancy enhancement in ZnO thin films through the surface modification using H-2 annealing. After H-2 annealing, low-temperature PL spectra show the strong emission at 2.5 eV and still observable at room temperature, in the same time PL spectra confirm the H-2 does not act as the impurity in our system. The Raman spectra show the dominance of oxygen vacancy as indicated by the emergence of A(1) (LO) mode. Moreover, X-ray photoelectron spectroscopy reveals that the number of oxygen vacancy on the surface is increased after the H-2 annealing. We found the strong relationship between oxygen vacancy and surface modification promoting strong green emission. Here, we propose the role of H-2 annealing in the surface modification leading to the formation of multiple-stacked porous ZnO film. This study also brings us to describe the electronic and optical transition mechanism. Our result is essential to improve the functionality of ZnO by surface modification for light-emitting device applications.