According to the measured formation pressure and typical profile pressure distribution characteristics, the authors find that the overpressure occurs in the lower-middle third Member and the fourth Member of Shahejie Formation in Dongying Sag. The authors analyze the paleo-pressure evolution using the Basin Modeling. The results show that the overpressure evolution mainly experiences three stages: original formation, meta-declining and latest-raising. Based on former analysis, overpressure is mainly caused by undercompaction, hydrocarbon generation and clay mineral transformation. The evolution of overpressure not only is well related with the hydrocarbon accumulation stages but also provides enough power.oft-com:office:office" />