Cu-based　catalysts　are　promising　candidates　for　CO2　reduction　owing　to　the　favorable　energetics　of　Cu　sites　for　CO2　adsorption　and　transformation.　However,　CO2　reduction　involving　insurmountable　activation　barriers　and　various　byproducts　remains　a　significant　challenge　to　achieve　high　activity　and　selectivity.　Herein,　a　photocatalyst　constructed　with　single-Ru-site-on-Cu-nanoparticle　on　Bi4Ti3O12　exhibits　exceptional　activity　and　selectivity　for　CO2　conversion　to　CO.　The　experimental　and　theoretical　results　consistently　reveal　that　the　Ru-Cu　dual　sites　allow　the　rapid　transfer　of　photogenerated　carriers　for　closely　interacting　with　CO2　molecules.　Importantly,　the　Ru-Cu　dual　sites　exhibit　extremely　strong　CO2　adsorption　ability,　and　the　Gibbs　free　energy　of　the　rate-determining　step　(*CO2　to　*COOH)　has　been　significantly　reduced,　synergistically　enhancing　the　entire　CO2　conversion　process.　The　optimal　BTOCu2Ru0.5　photocatalyst　manifests　a　high　performance　for　selective　reduction　of　CO2　to　CO,　yielding　10.84　mu　mol　over　15　mg　of　photocatalyst　in　4　h　(180.67　mu　molg(-1)h(-1))　under　a　300　W　Xe　lamp　without　any　photosensitizer　and　sacrificial　reagent,　outperforming　all　bismuth-based　materials　and　being　one　of　the　best　photocatalysts　ever　reported　under　similar　reaction　conditions.　This　work　presents　a　strategy　for　the　rational　design　of　multiple　metal　sites　toward　efficient　photocatalytic　reduction　of　CO2.