Methanol synthesis via carbon dioxide (CO2) reduction is challenging and important because this technology can convert CO2 by solar- or wind-generated hydrogen into liquid fuel. The present work introduces the visible light as an external stimulus and for the first time demonstrates that methanol synthesis over Cu/ZnO catalysts can be effectively promoted by solar energy under atmospheric pressure. Experimental and theoretical studies document that hot electrons were photo-excited by localized surface plasmon resonance (LSPR) on Cu nanoparticles and such photo-excited hot electrons could transfer to ZnO through the metal-support interfaces. The hot electrons on Cu and ZnO synergistically facilitated the activation of reaction intermediates. Consequently, the activation energy was reduced by 40% and the methanol synthesis activity was promoted by 54%. This work provides a new strategy towards synthesis of liquid fuel via CO2 reduction under low pressure and sheds new light on the mechanism of photo-mediated catalysis.