A research direction of using biochar to modify aqueous carbonated steel slag is proposed to address the issues of suppressed hydration activity and low CO₂ sequestration of steel slag. The results show that biochar effectively enhances the hydration activity and CO₂ reactivity of carbonated steel slag；and compared to samples that solely use carbide steel slag，the compressive strength of the active mineral slurry prepared through the synergistic use of biochar and wet-process carbide steel slay has increased by 21.5% at 7 d，with a 25.1% increase in CaCO₃ content. The synergistic effect of biochar and aqueous carbonated steel slag effectively refines the pore structure of the specimens， increases the amount of hydration products， and accelerates the early hydration heat release， thereby further improving the hydration activity of steel slag. The unique loose and porous structure of biochar facilitates the uniform precipitation of CaCO₃ in the pores of specimens， allowing for better nucleation and filling effects of CaCO₃.