<p>Input of biochar into soil is considered as an efficient technology for carbon sequestration. This work is aimed to explore if the extra sorption of carbon dioxide (CO₂) exists in the biochar-amended soil, which has not yet received attention. Here we put biochar and mineral-rich biochar into soils to perform laboratory CO₂ sorption experiments. Our results demonstrate that all biochar increased soil carbon storage and meanwhile further sorb CO₂ for more carbon sequestration. The Ca or Mg originated in biochar could react with more CO₂ and eventually be converted into inorganic carbonate minerals in the amended soil. Further, the country-level prediction showed that all cultivated top soils with biochar application in China could achieve 7.38–12.5 billion tons of carbon sequestration and an additional 0.34–2.66 billion tons of CO₂ sorption. The results require us to take into consideration of both carbon sink and extra CO₂ sorption in the assessment of biochar carbon sequestration potential in soil.</p>