Development characteristics of a fault system are an important manifestation of the structural evolution of the eastern Liaodong Bay Depression in the Cenozoic period. Based on plenty of three dimensional seismic data, this paper describes the horizontal decreased and sectional characteristics of fault systems in detail in the study area and analyzes the formation mechanism of the fault systems. The result shows that the fault systems in the Paleocene and the Eocene mainly consist of NNE trending extensional faults. And the fault systems in the Oligocene have the strike-slip characteristics. The vicinity of main faults has significantly stress-increased area and stress-decreased area due to the strike-slip effect. The flower-liking structures and“Y”-type structures can be observed in the seismic profiles. The secondary faults mostly consist of NEE trending en-echelon faults. The main faults and the secondary faults can form strike-slip duplex. In Neogene, the secondary faults are still manifested as NEE trending en-echelon faults and the fault system shows characteristics of weak strik-slip. And conjugate shear fractures and antiform-negative flower structures began to appear in this period. The study of the fault system illustrates the superimposition and transformation between extension tectonic systems and strike-slip tectonic systems in the eastern Liaodong Bay Depression in the Cenozoic. Combined with dynamic evolutionary mechanism of the Bohai Bay Basin, the evolutionary stages of the eastern Liaodong Bay Depression can be divided into the weak strike-slip-strong extension period (Paleocene-Eocene） , the weak extension-strong strike-slip period (Oligocene), and the weak compression-weak strike-slip period (Neogene).