Single atom catalysts (SACs) have been widely studied in the field of CO2 electroreduction, but industrial‐level current density and near‐unity product selectivity are still difficult to achieve. Herein, a diatomic site catalysts (DASCs) consisting of Co‐Cu hetero‐diatomic pairs is synthesized. The CoCu DASC exhibits excellent selectivity with the maximum CO Faradaic efficiency of 99.1 %. The CO selectivity can maintain above 95 % over a wide current density range from 100 mA cm−2 to 500 mA cm−2. The maximum CO partial current density can reach to 483 mA cm−2 in flow cell, far exceed industrial‐level current density requirements (>200 mA cm−2). Theoretical calculation reveals that the synergistic catalysis of the Co‐Cu bimetallic sites reduce the activation energy and promote the formation of intermediate *COOH. This work shows that the introduction of another metal atom into SACs can significantly affect the electronic structure and then enhance the catalytic activity of SACs. A diatomic site catalyst consisting of Co‐Cu hetero‐diatomic pairs is designed via a general and facile method. Industrial‐level current density can be easily achieved in a flow cell system with the maximum CO partial current density up to 483 mA cm−2. The CO selectivity can be maintained above 95 % over a wide current density range from 100 mA cm−2 to 500 mA cm−2.