Abstract: Traditional 3-D seismic data interpretation is a 2D interpretation based on 3D seismic data.Faults are picked from seismic sections along inline or crossline,in the mean time take time-slices as reference.Coherence data is just used to verify fault interpretation result.Automatic Fault Extraction is a process designed to automatically interpret fault surfaces from 3--D seismic discontinuity volumes according to its dip & azimuth changes in coherence data.Several processing steps are applied to the discontinuity volume to improve the imaging of fault surfaces,followed by processes to automatically track the fault lineaments on vertical and horizontal slices through the volume.Fault Extraction technique is applied to fault interpretation at Dabusu complex structure zone in southern SongLiao basin.Tiny faults are identified exactly,faults shape and faults contact is also ascertained clearly,fracture system is analysed rightly under 3D Visualization environment.That availably directs petroleumn exploration and deployment in Dabusu zone.