Efficient CO₂ photoreduction towards C₂₊ solar fuels has emerged as one of the most promising strategies for alleviating the current energy and environment problems. However, the C-C coupling barriers and complex multi-electron transfer steps still limit the activity and selectivity of CO₂-to-C₂ photoreduction. Herein, Au nanoparticles (NPs) modified CeO₂ with oxygen vacancies (Au/CeO₂-V_O) were reported for enhancing the CO₂-to-C₂H₆ photoreduction performance. Au/CeO₂-V_O achieved the high C₂H₆ activity of 51.7 μmol·g⁻¹·h⁻¹, accompanied with C₂H₆ selectivity up to 80% in the absence of sacrificial agent. Experimental results combined with theoretical simulation indicated that V_O strengthened CO₂ adsorption and activated *CO production, and plasmon-induced hot electrons from Au NPs to CeO₂-V_O facilitated the *CO-*CO dimerization. The synergistic modulation of V_O and hot electrons further decreased the energy barriers of C-C coupling and subsequent hydrogenation, resulting in the superior photoreduction performance. This work opens an avenue of developing plasmonic photocatalysts for multi-carbon products from CO₂ photoreduction.