Abstract: Based on the soil CO₂ concentration in the south of Tangyin graben determined by gridding layout sampled points in the field, the factors affecting the spatial distribution of soil CO₂ concentration are analyzed, and the relationship between spatial distribution of soil CO₂ concentration and geological structure are revealed. The results show that the soil CO₂ concentration in the south of Tangyin graben is between 0.07% ~ 5%, the background value is 0.6%, and the anomaly threshold is 2.35%.The soil CO₂ concentration in the south of Tangyin graben is higher in the east-central regions than that in the western, which is corresponds to trendy of sedimentary layer thicker from west to east in the study area. The high-value of soil CO₂ concentration in the east-central regions is mainly distributed along the fault zone. The activity of Tangdong fault is the strongest, while that of Tangxi fault and Tangzhong fault are weak. The main factors affecting the soil CO₂ concentration are fracture structure, sedimentary layer and vegetation. The high-value points of soil CO₂ concentration are mainly distributed along the faults, indicating that the active faults are the channels of gas release from the earth's interior, and the CO₂ is an effective tracer for tectonic activity.