Abstract: In order to further understand the distribution pattern of the Gaojiabian Formation in the Lower Yangtze areas and its implications for the South Yellow Sea Basin, collection and analysis of previous data, field geological investigation, and correlations of outcrop and drilling cores samples have been carried out. The results show that the source rocks in the Gaojiabian Formation are widely distributed. The yellowish green outcrops of the Gaojiabian Formation should be black before weathering. The original abundance of organic matters might be higher. The exclusive graptolites of the Rhuddanian stage have been discovered in the Gaojiabian Formation, indicating high hydrocarbon-generating potential. In consideration of the regional tectonic evolution of the Lower Yangtze areas and upon the seismic profile interpretation of the South Yellow Sea Basin, it is concluded that the Gaojiabian Formation could be a suit of excellent source rocks widely distributed with high organic matter abundance.