Abstract: Xiadian fault in east part of Beijing is an active baspment fault for a long time. It is characterized by the syngenetic fault. The index of growth during early pleistoceac-middle pleistocene was 2.2-2.1. Since late upper pleistocene it is 2.7. This showed increasion of the fault's activity. To study activity of Xiadiin fault, Sporo-pollen analysis, micro-paleonotology and radiocarbon ¹⁴C dating were carried out for rocks in two borehole on two sides of the fault. It is shown that there is not Holocene epoch stratum in two sides of the fault. So we concluded that total uplift velocity has been more than differential movement velocity in the region since Holocene epoch. Xiadjan town lies to a intersecting point of NNE, NW and EW trend active faults, Especially, it is noted that Xiadian fault was cut by Sunhe fault of NW trend. Sine late upper pleistocene epoch, the growth index of Sunhe fault has bsen incrsaded from 1.4 to 2.0. It corresponds with Xiadian fault. Under above geological structure background, an earthquake (8.0) occurred along Xiadian fault in 1679, The epicenter showed be located near Xaidian town.