Abstract: Abnormal geotemperature-pressure (T-P) systems of Xihu sag in East China Sea shelf basin, based on the data of geotemperature by using well drilling and pressure by using acoustic transit time, in-clusions, vitrinite reflectivity and apatite fission track, and their characteristics, types and effects on reservoir formation are systematically analyzed during the study. The result shows that characteristics of T-P systems in different tectonic units are distinct. There are two types of T-P systems, overpressure type in the Baoshu slope belt and Santan deep sag, and normal-pressure type in the Zhedong central anticline belt. For different T-P systems, fluid flow styles and hydrocarbon migration laws are different. The fluid energy in the Zhedong central anticline belt, which is the best hydrocarbon migration region in Xihu sag, was relatively lower than any other tectonic units.