Based on the data of DST and FMT, the distribution and evolution characteristics of overpressure in Northern Liaozhong subdepression are analyzed by applying interval transit time and numerical simulation method. It is suggested that overpressure is extensively developed in the basin. The reservoir overpressure which the max pressure coefficient is 1.93, is mainly developed in Paleogene formation and buried hill formation. The undercompaction is extensively developed in Lower Dongerxia Formation and the calculated pressure coefficient can reach 1.9 and more. Compaction disequilibrium resulted of high sedimentary rate and hydrocarbon generation are main factors for the development and evolution of overpressure in shale intervals, while the main mechanism of reservoir overpressure is the migration and charging of the overpressure fluids from source rock in the centre of subdepression. Overpressure developed since the Shahejie Formation deposits and increased gradually until the end of Dongying Stage, then decreased. From Mingxia Formation deposits, overpressure increased once more and reached the maximum now. This paper studied the characteristics of fluid inclusions and geothermal with pressure in reservoirs, the history of hydrocarbon generation and maturity of oil and gas, the physical properties of petroleum. It is suggested that the process of petroleum accumulation is episodic and late rapid. The migration of petroleum along the faults is limited as the development and activities of faults is weak. Hydraulic fracture caused by overpressure developed in source rock is the major conduit for episodic hydrocarbon expulsion; meanwhile, overpressure is a favorable power for long lateral hydrocarbon migration. It is suggested that overpressure dominated controlled episodic and late rapid petroleum accumulation.