Choosing special materials to achieve good adsorption and capture of CO₂ is an essential technique for solving the problem of global warming. Biochar is an ideal precursor CO₂ adsorbent due to its renewability, stability, and useful physicochemical properties. Furthermore, heteroatom doping can significantly improve the characteristics of biochar, such as enrich heteroatom functional groups and regulate carbon skeleton. This study reviews existing heteroatom doping methods and summarizes the current understanding of the influence of heteroatoms on CO₂ adsorption of biochar. Specifically, compared with different doping methods, pre-decoration doping has higher doping efficiency and creates more abundant surface functional groups than post-decoration doping. Considering multi-element co-doping can combine the special functions of each element, application advantages and potential problems of co-doping are analyzed. In addition, the study further revealed that difficulty level with heteroatom doping mainly depend on the atomic structure of the doping element. The further improvement of chemical adsorption while ensuring optimal physical adsorption will become the research focus of atom-doping-modified, biochar-based, CO₂ adsorbents in the future. We believe that these summaries are valuable for systematically understanding heteroatom-doped biochar to CO₂ adsorption and will serve as a theoretical support for heteroatom doping research.