Abstract: The Liaodong south sub?sag in Bohai Bay basin is an area with shallow burial, complicated structural evolution, low exploration degree, and unclear resource potentials up to now, so evaluation of the source rocks in this area is extremely necessary. Based on geochemical and paleontological analysis, the main hydrocarbon?generating sequences are determined in this south sub?sag. It is considered that the Sha?1 to Sha?3 members of the Oligocene Shahejie formation are of high abundance and good type of organic matter as well as high maturity of source rocks, which could be as the major source rocks in the study area; the Sha?4 member to Kongdian formation are of relatively low abundance of organic matter with relatively high maturity and extensive distribution, which could be as the potential source rocks; the Dong?3 member of the Oligocene Dongying formation has relatively low maturity of the source rocks, so it provides less contributions to hydrocarbon generation. Based on logging data and multi?attribute seismic inversion processing, quantitative evaluation is made for each high?quality source rock development scale, and the result shows that several series of source rocks exist in the south sub?sag, which are widely distributed and have greater hydrocarbon?generating potentials, most being of petroleum exploration prospect. The high?quality source rocks in the north part of it are significantly thicker than that in the south part, which is the hydrocarbon?generating center in the study area. The source rocks in the south part are in beaded distribution along the strike?slip fault and controlled by the fault