The incorporation of guest elements into Cu-based bimetallic oxides has been proven as an effective way to modify the electronic structure and reactivity of Cu active sites. Here, the Y element was chosen as the guest element to modulate the electronic structure of Cu and alter its performance for electrochemical CO2 reduction reaction (CO2RR). Y2Cu2O5, a high-crystallinity Cu-based bimetallic oxide, was synthesized via the sol–gel method. For pure-phase CuO and Y2O3 controls, the selectivity of H2 significantly exceeded that of CO. While Y and Cu combined in equal molar weights to form Y2Cu2O5, a notable enhancement in the CO selectivity was observed, resulting in a CO/H2 ratio of approximately 1:1. These results prove that under the influence of Y, the electronic structure of Cu exhibits heightened CO selectivity. When the electrolyte solution was substituted with 1 M KOH, the CO/H2 ratio achieved was about 2:1, indicating that the ratio of syngas can be adjusted by changing the concentration or type of electrolyte. This study explores the electronic modulation of a guest element in Cu-based bimetallic oxides and clarifies the beneficial influence of the Y element on the activity of Cu sites, which provides a novel approach for designing and regulating the activity of catalyst active sites.