Abstract: Hydrocarbon exploration has been conducted in South Yellow Sea Basin for nearly 30 years, with Mesozoic-Cenozoic strata as the main exploration targets, but no commercial oil & gas flows have been discovered. The degree of exploration in Mesozoic -Paleozoic is still very low, and the Mesozoic-Paleozoic strata were penetrated only in a few wells. Therefore, the understandings about the basic geologic conditions in Mesozoic-Paleozoic strata are still poor. On the basis of the petroleum system theory, with well drilling data and using basin modeling techniques, comparion has been conducted with the study results about the geologic conditions in the Lower Yangzi continental areas, and a preliminary study about the petroleum geologic conditions for HC accumulation, mainly source rocks, reservoirs and seals in Mesozoic-Paleozoic marine strata in the Lower Yangzi areas of South Yellow Sea Basin has been finished, and favorable exploration targets for next exploration in Mesozoic-Paleozoic have been proposed.