Because of its rich oil and gas resources and the special tectonic location of the Liaohe Western Sag (the Tanlu Fault traverses the sag),Bohai Bay Basin,a detailed study of its strike-slip tectonics is significant in revealing the sag’s tectonic evolution,its control on hydrocarbon accumulation, and the activity history of the northern section of the Tanlu Fault in the Cenozoic.Through systematic structure analysis of 3D seismic data of the Liaohe Western Sag,combined with balanced section analysis, a variety of structural features in relation to right-lateral strike-slip faults,such as echelon normal faults,“comb”structure,“flower”structure,“interpretable”and“buried”strike-slip faults have been revealed exist in the Liaohe Western Sag.According to the research in this paper,the complex structural phenomena in the Liaohe Western Sag could be reasonably interpreted as right-lateral strike-slip activity and the strike-slip activities of the Liaohe Western Sag began in the early Oligocene.The activity was weak at the beginning (E_(3S1-2)),then strengthened gradually and reached its strongest level in the late Oligocene (E_(3al)).In the Miocene,the strike-slip activity was low and then strengthened significantly once again from the Pliocene to the present.It is speculated that the entire northern section of the Tanlu Fault has had a similar evolution history since the Oligocene. Because of its rich oil and gas resources and the special tectonic location of the Liaohe Western Sag (the Tanlu Fault traverses the sag), Bohai Bay Basin, a detailed study of its strike-slip tectonics is significant in revealing the sag’s tectonic evolution, its control on hydrocarbon accumulation, and the activity history of the northern section of the Tanlu Fault in the Cenozoic. System structure analysis of 3D seismic data of the Liaohe Western Sag, combined with balanced section analysis, a variety of structural features in relation to right -lateral strike-slip faults, such as echelon normal faults, “comb ” structure, “flower ” structure, “interpretable ” and “buried ” strike-slip faults have been revealed exist in the Liaohe Western Sag. According to the research in this paper, the complex structural phenomena in the Liaohe Western Sag could be reasonably interpreted as right-lateral strike-slip activity and the strike-slip activities of the Liaohe Western Sag began in the early Oligocene. The activity was weak at the beginning (E_ (3S1-2)), then stepped gradually and reached its strongest level in the late Oligocene (E_ (3al)). In the Miocene, the strike-slip activity was low and then strongly dominant once again from the Pliocene to the present. It is speculated that the entire northern section of the Tanlu Fault has had a similar evolution history since the Oligocene.