Carbon capture and storage (CCS) has substantial potential for deep decarbonization of the steel sector. However, long-term transformations within this sector lead to significant changes in steel units, posing challenges for CCS deployment. Here, we integrate sector-level transformation pathways by 2060 to simulate the distribution of China’s steel units and generate optimal CCS deployment schemes using a source-sink matching model. Results indicate that CCS accounts for 31.4-40.7% of carbon mitigation effects in China’s steel sector by 2060. Following the sector-level pathways, over 650 steel units will either be eliminated or retrofitted. The optimal CCS deployment schemes can achieve carbon mitigation effects of 472.4-609.6 Mt at levelized costs of 187.4-193.5 Chinese Yuan t⁻¹ CO₂, demonstrating cost-effectiveness under future carbon price levels. Nevertheless, the proposed schemes will lead to energy and water consumption of 951.0-1427.3 PJ and 1.60-1.69 million m³, respectively, posing a risk of resource scarcity. These insights inform the development of CCS implementation strategies in China’s steel sector and beyond, promoting deep decarbonization throughout society.