The unhydrated and hydrated MgAl supported Cu catalysts were successfully prepared by metal-organic chemical vapor deposition (MOCVD) method. The structure properties of metal-organic precursor, supports and catalysts were determined by H-1 NMR, FTIR, XRD, N-2 physisorption, TEM, N2O titration, and CO2-TPD. The hydration of support had a significant effect on the structure of the final catalysts. The hydrated Mg3Al1 support was benefited to the adsorption and deposition of Cu-II(hfac)(2), resulting in the decrease of the reduction decomposition temperature. Due to the restoration of the layered structure, the 5%Cu/H-Mg3Al1 catalyst had a low BET surface area and pore volume. However, it exhibited higher base sites density and got better performance for cellulose hydrogenolysis compared to the 5%Cu/Mg3Al2 catalyst, which suggested that the hydration before reaction was superior to that during reaction for the catalytic performance, due to the competition between water and products (alcohols with strong adsorption) during reaction, resulting in a decrease in the concentration of in-situ formed surface OH- and the amount of base sites. It was noteworthy that unobvious change in phases of the 5%Cu/H-Mg3Al1 catalyst was observed before and after reaction, which provided a promising way to establish the relationship between structure and catalytic performance.