Abstract: Concealed faults are developed in the Beijing area. They intersect with NW- and NE-trending faults, forming a potential tectonic background of earthquakes in the future. To study the relationship between active faults and the radon concentration in soil, this study measured the radon concentration of two profiles (NW- and NE-trending) in plain areas of Beijing. Through tests and analysis, this study roughly ascertained the relationship between concealed structures and the radon concentration in soil, as well as the geological factors influencing the radon concentration of soil. The results show that the radon concentration in areas with active faults is significantly higher than that in the surrounding areas, and the radon concentration in areas with complex structure and highly active faults changes more noticeably. The depth of Cainozoic strata constrains the dissipation of radon to a certain extent, and there is a positive correlation between the depth of Cainozoic strata and the radon concentration in soil. The specific activity of radionuclides in parent rocks with different soil quality also affects the background value of regional radon concentration. The results of this study determined the relationship between concealed faults ahe specific activity of radionuclides in parent rocks with different soil quality also affect the background value of regional radon concentration. The results of this nd the radon concentration in soil and identified the influence of the thickness of Cainozoic strata and parent rocks with different soil quality on the radon concentration in soil, thus serving as an important reference and guidance for the surveys of concealed faults and the research on radon concentration in plain areas of Beijing in the future.