Abstract:The Taihu segment of the Tanlu fault zone lies on the east side of the Dabie mountains. It is the tectonic boundary between the Dabie mountains and the foreland basin, and the linear features of the faults are clear on remote sensing images. Geological surveys and trench work were carried out in the Taihu-Tongcheng area. In the Taihu trough we find a soft fault gouge in the fault zone, and the fault extends upward into the middle Pleistocene clay. Test results of OSL and ESR show that faults have strong activity in the middle Pleistocene.The fault profile of the Honglaowu in Tongcheng shows that the fault has broken the early Pleistocene gravel layer, and the fault gouge developed in the lower part of the fault. ESR sample test results also show that the fault has a strong activity in the middle Pleistocene. According to comprehensive analysis, it is concluded that the Taihu segment of the Tanlu fault zone still has a strong activity in the early Pleistocene, and the latest activity is the middle Pleistocene (Q2), which is a tectonic background factor mainly composed of small and medium-sized seismic activity in the study area.