Abstract: Controlled by the Tanlu strike-slip fault zone, a unique strike-slip and extensional composite fault system is developed in the Bohai Sea area, from which a large number of complex fault block traps was formed. At present, it is difficult to quantitatively evaluate the true lateral sealing ability of faults by traditional methods. The mechanical properties of the faults are so complex that the capacity of side sealing is difficult to be quantitatively evaluated. Therefore, using the Lvda A area of Liaodong Bay depression as an example, on the basis of logging identification of fault fracture zone, interval transit time was used to judge fault mechanical properties. The stress coefficient λ was proposed to quantitatively correct the influence of fault properties on lateral sealing ability. Finally, a simplified fault-reservoir displacement pressure difference method was used to quantitatively evaluate the true lateral sealing ability of fault blocks, and to quantitatively predict the height of oil column of fault blocks.