This paper describes the origin of the reactivity and stability of boron-modified copper-based catalysts with prolonged lifespan for the vapor-phase selective hydrogenation of dimethyl oxalate to ethanol. Display omitted ► A low-cost copper-based catalyst for synthesis of ethanol with high efficiency. ► Boron modification is a readily available approach for improving the stability. ► Boron could improve the copper dispersion and suppress the growth of Cu particles. ► Boron affects the acidic/basic sites and enhances the metal–support interaction. The long-term stability and activity of catalysts are vital for vapor-phase selective hydrogenation of dimethyl oxalate to synthesize ethanol. Boron has been widely employed as a modifier for transition-metal catalysts mainly to, improve selectivity and stability. We introduced boron species by impregnation into silica-supported copper catalysts prepared by an ammonia evaporation hydrothermal method and investigated their catalytic activity and thermal stability for hydrogenation of dimethyl oxalate. The effect on activity mainly depends on the amount of boron and an optimal Cu/B molar ratio of 3 was obtained. The characterization of the catalysts shows that boron-modified Cu/SiO2 facilitates the dispersion of copper species, enhances the metal–support interaction, and suppresses the growth of copper particles during dimethyl oxalate hydrogenation.