The western of Liaohe depression, which is rich in oil and gas resources and located in the Bohai Bay Basin, with the Tanlu fault crossing through the depression, offers a good opportunity to make an indepth investigation of its strikeslip structure, tectonic evolution and oil accumulation controlling, and action history of the northern section of the Tanlu fault during the Cenozoic. Through a systematic structural analysis of 3D seismic data in the westert Liaohe depression, combined with sand box modeling, this study reveals existence of a variety of structure signatures relevant to strikeslip in the depression, including echelon normal faults, "comb" structure, flower structure, and so on. The paper believes that the strikeslip of the depression initiated in the early Oligocene (E3s1－2), gradually intensified and reached the culmination at the end of Oligocene (E3d1). It was less action in the Miocene and, since the Pliocene time, it has been gradually active up to now. It is speculated that the north section of Tanlu fault underwent similar evolution after Oligocene. Sand box modeling test also indicated that under the condition of strikeslip pull, about twothirds of the strikeslip displacement was turned into extensional displacement and estimation for cumulative rightlateral strikeslip displacement in the depression is about 18 km since Oligocene, in which the displacement is 10.5 km in the Oligocene (E3s1－2－E3d), 1.8 km in the Miocene (N1g) and 5.7 km in the the Pliocene epoch(N2m－Q), with average strikeslip speeds of 0.71mm/a, 0.10 mm/a and 1.11mm/a respectively.