Supported gold nanoparticles are highly selective catalysts for hydrogenation of acetylene, but low activity and heavy coke effect have been major concern for the Au-based catalysts. Based on a modified impregnationcalcination strategy, a series of MgOx-Al2O3 composite oxides with different crystal structures from mixed phase to pure spinel was prepared. Due to its crystal defect and synergetic effect, Au nanoparticles on MgOx-Al2O3 components treated at 550 degrees C (abbreviated as Au/3%MgOx-Al2O3-550) with well controlled smaller particle size gave an enhanced activity for the selective acetylene hydrogenation. The conversion rate was nearly twice as high as that of all other samples at 250 degrees C. The H-2-TPR and XPS results indicate the partially positive charged Au species (Au8+) played a crucial role in facilitating the adsorption of the C C group. Both the temperature programmed oxidation and Raman scattering also indicated that the Au/3%MgOx-Al2O3-550 showed better decoking effect than Au/Al2O3. This report opens up promising possibilities on engineering the crystal phase of support for the highly efficient heterogeneous gold catalysts.