Photocatalytic reduction of carbon dioxide (CO) is attractive for the production of valuable fuels and mitigating the influence of greenhouse gas emission. However, the extreme inertness of CO and the sluggish kinetics of photoexcited charge carrier transfer process greatly limit the conversion efficiency of CO photoreduction. Herein, we report that the plasmonic coupling effect of Pt and Au nanoparticles (NPs) profoundly enhances the efficiency of CO reduction through dry reforming of methane reaction assisted by light illumination, reducing activation energies for CO reduction ∼30% below thermal activation energies and achieving a reaction rate 2.4 times higher than that of the thermocatalytic reaction. UV-visible (vis) absorption spectra and wavelength-dependent performances show that not only UV but also visible light play important roles in promoting CO reduction due to effective localized surface plasmon resonance (LSPR) coupling between Pt and Au NPs. Finite-difference time-domain simulations and in situ diffuse reflectance infrared Fourier transform spectroscopy further reveal that effective coupling LSPR effect generates strong local electric fields and excites high concentration of hot electrons to activate the reactants and intermediate species, reduce the activation energies, and increase the reaction rate. This work provides a new pathway toward the efficient plasmon-enhanced chemical reactions via reducing the activation energies by utilizing solar energy.