Abstract: QiongDongNan Basin is characterized by high geotherm and geopressure. Its average geothermal gradient is higher than 4℃/100m. The factors influencing the geothermal field include volcanic activity, Moho depth, fault activity and lithology. The unique geotherm-pressure field controls the hydrocarbon evolution and distribution. Now, the issue of overpressure has become the hot issue. This paper, using description of "three fields", is to say the relationship between overpressure and distribution of oil and gas.