Abstract: The Unique geological evolution of the Yinggehai basin resulted in more than three sets of thick muddy deposits. subsequent compaction of the sediments and differential discharge of fluids from the pores led to the existence of large scale overpressure systems. Formation of large amount of hydrocarbons and high heat flow reinforced the overpressure. Diapirism made the overpressure propagate upwards. As a result,the overpressure systems were developed in the well-dinpired central part of the basin,where the top of the system rises to a depth of 2000~3000m and slopes towards the margins. The episodic release of the overpressure may cause an upward migration of the oil and gas to shallow depth to accumulate into pools.