Catalysts featuring multiple active sites hold significant potential for CO2 photoconversion to multi-carbon products. However, multi-metal-site catalysts typically face challenges with low yields and selectivity for ethylene production, with a lack of definitive design guidelines. Here we show that Bader charge can serve as a critical descriptor for delineating the structure–activity relationship of kesterite-like nanosheets in the reduction of CO2 to ethylene. We propose the Bader-Regulate-Performance principle — apposite Bader charge can provide a moderate energy barrier for intermediate adsorption and C-C coupling simultaneously, thus promoting the performance for ethylene generation. Among the predicted multi-metal-site nanosheets, the Cu2ZnSnS4, with the appropriate Bader charge, achieves a high ethylene yield of 25.16 µmol g−1 h−1 with electron selectivity of 72.4% under visible light irradiation, surpassing those of reported photocatalysts under similar catalytic conditions. Our findings provide crucial insights into the design of efficient catalysts for photocatalytic CO2 conversion to multi-carbon products.