Abstract: Electrocatalytic carbon dioxide (CO₂) reduction is an important way to achieve carbon neutrality by converting CO₂ into high-value-added chemicals using electric energy. Carbon-based materials are widely used in various electrochemical reactions, including electrocatalytic CO₂ reduction, due to their low cost and high activity. In recent years, defect engineering has attracted wide attention by constructing asymmetric defect centers in the materials, which can optimize the physicochemical properties of the material and improve its electrocatalytic activity. This review summarizes the types, methods of formation and defect characterization techniques of defective carbon-based materials. The advantages of defect engineering and the advantages and disadvantages of various defect formation methods and characterization techniques are also evaluated. Finally, the challenges of using defective carbon-based materials in electrocatalytic CO₂ reduction are investigated and opportunities for their use are discussed. It is believed that this review will provide suggestions and guidance for developing defective carbon-based materials for CO₂ reduction.