Abstract: Carbon Dioxide Geological Utilization and Storage (CGUS) is an important technological component in implementing China's "dual-carbon" goals and ensuring energy security.The evaluation of storage effectiveness is an integral part of the CGUS system,spanning the entire project lifecycle.This paper,based on soil CO₂ flux monitoring and analytical methods,conducted a soil leakage monitoring study in a CGUS demonstration project in the Junggar Basin.It analyzed the influencing factors on soil CO₂ flux testing and discussed regional flux differences and potential leakage pathways.The study results indicate that soil testing depth,testing duration,ambient temperature,and in-situ removal of surface loose soil are key factors affecting soil CO₂ flux.The effect of ambient temperature should be considered when calculating emissions at different times.The soil CO₂ flux around the single well area was relatively high,with an average CO₂ emissions within 1 m of the wellbore being about 8 times that of the background areas,indicating that the wellbores are currently the main pathway for CO₂ leakage.During the monitoring period of the demonstration project,the regional soil CO₂ fugitive emission was 372.89 kg/d,and the annual CO₂ fugitive emission accounted for approximately 0.14% of the injected volume,suggesting minimal environmental impact.This study provides a good technical practice for CGUS soil flux monitoring and evaluation,which is of great significance for the effectiveness and safety assessment of the project.