Abstract: The stereo characteristics of the focal faults of strong earthquakes are described by seismic data (isoseismic, surface rupture zones, ground deformation, plane and section distribution of aftershockst and focal mechanism).It has been found that the upper bound of the focal fault is the G interface obtained by seismic sounding data and is consistent with the high—dip angle deep fault beneath the interface, which proved that the deep fault underwent a shere disturbance during the earthquake.The focal fault and the listric normal fault on G interface formed two sets of disconnected fault systems, there are corresponding and ancorresponding relations between them.