The Suqian segment of the Tanlu fault has been a focus area of Jiangsu earthquake for many years. Multiphase active fault detection and engineering seismic safety evaluation have been carried out in this area. In addition, many earthquake monitoring methods have been established, such as seismometry, deformation, electromagnetic, and fluid, among others. It is of great significance to study the relationship between active fault movement and earthquake occurrence using gas geochemical method. The two main faults (F_5-1 and F_5-2) composing the fault F₅ in Suqian section of the Tanlu fault are inclined to each other and developed nearly vertically. In this paper, five survey lines of soil radon were set up along the fault F₅. Combined with the data of geological survey and shallow artificial earthquake, the results showed that the detection results of soil radon in the study area have a clear indication for the fault location, fault type and characteristics, and fault activity. Soil radon detection shows the location of fault F_5-1 and fault F_5-2. There is a certain correspondence between the abnormal shape of radon concentration and the characteristics of fault. The relative activity of the two branch faults of F₅ fault in the Suqian section of the Tanlu fault zone is preliminarily judged using the concentration intensity of soil radon as index.