Abstract: CO₂ environmental impact monitoring technology is an important part of the Carbon Capture, Utilization and Storage (CCUS) system, which runs through the entire storage process and determines the success of CCUS. This technology also plays a decisive role for the effectiveness, sustainability, safety of the CCUS project and the assessment of carbon emission reduction effects. It is necessary to carry out the full-process measurement and monitoring of multiple monitoring indicators, such as environmental capacity, stratum response, and CO₂ underground migration, in order to ensure the safe and reliable operation of carbon storage projects. The emphasis of CO₂ environmental impact monitoring will be different under different monitoring stages and different monitoring indicators, and the corresponding monitoring technology combinations will show slight difference. Focusing on the CO₂ leakage monitoring and leakage source monitoring and identifying, the authors have systematically analyzed the features and application scenarios of CO₂ environmental impact monitoring technology, and expounded on the CO₂ environmental impact monitoring technology research progress under different monitoring stages and different monitoring indicators. Besides, the authors have also summarized CO₂ environmental impact monitoring technology selections under different leakage scenarios and the practical problems, and pointed out that the research and development of real-time monitoring equipment, the atmosphere-surface-underground three-dimensional rapid monitoring technology system and the construction of long-term and effective CO₂ monitoring management system would be the future development direction of the CO₂ environmental impact monitoring technology, which could provide some reference for the development of environmental impact monitoring technology for future megaton-level carbon storage projects.