Abstract: Seismic reflection exploration is the main method of detecting urban active faults at present.The effect of investigating fault is fairly satisfactory in areas with thick Quaternary sediments.Detecting active faults by the seismic method is more difficult because of a-dopting shorter receive array length,more serious source disturbance to shallow reflection interference,and requiring higher resolution in urban shallow Quaternary sediment areas.Geziwo fault in Beidaihe is part of Qinhuangdao-Dalian fault on land.Because the fault is a hidden fault,the dip,fault distance and upper break point as well as spatial distribution of the fault all show uncertainty. In order to find out the spatial distribution shape,nature and activity of the fault,the author detected the fault by shallow seismic exploration technology with high precision,with the obtaining of a very clear reflection seismic image.The Quaternary internal interface,bedrock and bedrock weathering layer as well as fracture structure can be explained on the basis of the seismic profiles.The seismic detecting result provides the basis for the layout of the drilling joint section,the design of borehole depth and the evaluation of the fault activity.The high-preci-sion combined drilling geological sections show that the main stratigraphic boundaries and fault features obtained from the seismic explo-ration methods are quite consistent with the results from the composite drilling geological section.