Abstract: The Jurassic is critical important in geotectonic studies and oil-gas researches in China. Based on the newly drilled well S1 in the north-east sag of the northern depression of the South Yellow Sea, this paper analyzed the lithologic associations and the sporo-pollen assemblages of the cores. It is confirmed that target formation is Jurassic. It means that there was a Jurassic sedimentary basin occurred in the South Yellow Sea, which bears great potential of the Mesozoic deposits. It is further confirmed that the South Yellow sea basin was a foreland basin owing to the collision between Yangtze plate and North China plate during the Iindo-Sinian and Yanshan stages. The discovery of the Jurassic strata and tectonic evolution analysis will provide enlightenment for the study of tectonics in the South Yellow Sea and peripheral basins of the Lower Yangzi areas.