Abstract: Steelmaking industry faces urgent demands for both steel slag utilization and CO₂ abatement. Ca and Mg of steel slag can be extracted by acid solution and used to prepare sorbents for CO₂ capture. In this work, the calcium-based sorbents were prepared from stainless steel slag leachate by co-precipitation, and the initial CO₂ chemisorption capacity of the calcium-based sorbent prepared from steel slag with the Ca and Mg molar ratio of 3.64:1 was 0.40 g/g. Moreover, the effect of Ca/Mg molar ratio on the morphology, structure, and CO₂ chemisorption capacity of the calcium-based sorbents were investigated. The results show that the optimal Ca/Mg molar ratio of sorbent for CO₂ capture was 4.2:1, and the skeleton support effect of MgO in calcium-based sorbents was determined. Meanwhile, the chemisorption kinetics of the sorbents was studied using the Avrami-Erofeev model. There were two processes of CO₂ chemisorption, and the activation energy of the first stage (reaction control) was found to be lower than that of the second stage (diffusion control).