Electrochemical reduction of carbon dioxide (CO2) has triggered significant interest recently. However, it still suffers from low selectivity and poor lifetime. Herein, light illumination was introduced and the catalytic activity of copper nanowires was investigated in the CO2 reduction. It was found that carbon monoxide showed an obvious light enhancement effect and it got the highest enhancement at −1.0 V versus reversible hydrogen electrode while the light enhancement of methane was limited. Light illumination was also found to be able to increase the lifetime of the copper catalyst. These interesting results indicate the existence of significant effects of light in this system and have shown the potential for light to interfere the pathway of CO2 reduction. Further work is also proposed in detail to explore the mechanisms.