Abstract: The NW-SE trending Xiaofeng-Sanmen fault (XSF) is a major fault in Hangzhou region. The XSF is of left-lateral strike-slip character since late Quaternary and dislocated the NE trending Xiaoshan-Qiuchuan fault (XQF) and the EW trending Changhua-Putuo fault (CPF). These three faults meet together in Hangzhou region and make the Qiantang River turn around.Along the XSF, there are several earthquakes (M≤5) took place at the intersection area with the NE trending fault. Because of strong weathering, the geomorphological traces related to faults are hardly to be found and measured. Based on the observation of outcrops and geophysical exploration, four trenches were excavated on XSF in Hangzhou Region. These trenches exposed that the EW and NE trending faults were active along the XSF. These fault movements might be triggered by the activities of XSF which made the pre-existing fracture active in the Late Quaternary. The fault movements reduced the stress along the XSF and depressed the seismic risk for the Hangzhou region. Optically stimulated luminesence (OSL) samples of sediments were collected trying to get timing of the fault movements. The OSL ages are validated by sporopollen analysis. According to the OSL ages, the timing of fault movements could be grouped into two periods: (16.5~19.7) ka BP and (42.0 ~ 51.2) ka BP. The fault activities of XSF during the Late Quaternary are very important for regional seismic risk assessment.