Abstract: As the main greenhouse gas, CO₂ has a great impact on the global ecosystem. Biochar is considered to be a cost-effective CO₂ adsorbent because of its wide sources of raw materials and low preparation cost. However, the original biochar has poor structural characteristics and surface chemical properties, so its physical and chemical properties need to be adjusted. Based on the physicochemical properties of biochar, the preparation and modification methods of biochar were systematically analyzed in this paper. On the basis of previous studies, the mechanism of CO₂ adsorption by biochar was summarized. The influence of the changes of pore structure and surface chemical properties of biochar on its CO₂ adsorption performance during modification was emphatically expounded. In addition, the possible problems of biochar as CO₂ adsorbent in large-scale CO₂ capture and the main research directions in the future were also discussed, aiming at providing theoretical basis for the preparation and application of modified biochar CO₂ adsorbent.