Abstract: CO₂ geological storage in deep saline aquifers is an important supporting technology to achieve the goal of carbon neutrality in China, and it is also a technology of deep underground space development and utilization. The deep underground space for CO₂ geological storage in deep saline aquifers should be comprehensively evaluated on the basis of three-level boundaries, including CO₂ plume, perturbation boundary and economic condition. In this paper, the only deep saline aquifers storage project in China—the Ordos CCS demonstration project of National Energy Group have been taken as a case study. Based on the monitoring of CO₂ plume at the storage site and the prediction of perturbation boundary and the prediction of perturbation boundary, the authors have comprehensively affirmed that the 4 basic units of latitude 1' × longitude 1' of the project could be utilized as the boundary of CCS demonstration project. While the top of Zhifang Formation (about 958 m in depth) could be the top boundary, and the seal depth of 2 800 m is the bottom boundary of storage body in vertically. The method of developing deep underground space for CO₂ geological storage, proposed in this paper could provide references for the scientific planning and policy enacting in management. However, this method still needs to be further improved in combination with the existing laws and regulations and the future practice of large-scale storage projects.