Methanol steam reforming (MSR) is an attractive approach to produce hydrogen for fuel cells. Due to the limited catalyst loading volume and frequent start-ups and shut-downs on board, it is highly desired to develop an extremely active and robust catalyst. Herein, on the basis of industrial Cu/ZnO/Al₂O₃ catalysts, a series of CuZnAl-xMg catalysts with enhanced Cu-ZnO synergy were synthesized via magnesium assisted strategy. The incorporation of magnesium was found to be beneficial to the enhancement of catalytic activity and stability of catalyst. A combination of complementary characterizations (e.g. XRD, H₂-TPR, N₂O chemisorption, TEM, XPS analysis etc.) proves that isomorphous substitution of Cu²⁺ in malachite phase gives rise to more dispersive Cu and ZnO NPs, and the increased Cu⁺/Cu⁰ ratio indicates the strengthened Cu-ZnO synergy effect, which leads to the boosted stability during the thermal treatment.