Abstract: New exploration areas, deep formation and deep water, which belong to the low exploration activity fields, are important for petroleum exploration. Prediction for the thickness of source rocks is critical to the source rock evaluation in new exploration areas in sedimentary basins. In the research context of preliminary evaluation on source rock of the northeast sag, which is the new exploration area in South Yellow Sea basin at present, this paper tries to trace the main formation and dimensional distribution of major source rocks in northeast sag based on the seismic reflection characteristics. The method of seismic attribution is applied for the first time to the prediction of the thickness of major source rocks (upper Cre-taceous Taizhou formation and Palaeocene Funing formation) in northeast sag, which is tested by the method of seismic velocity-lithology prediction to estimate the thickness of Taizhou formation source rock. We suggest that Taizhou formation source rock is widespread with larger thickness in northeast sag than Funing formation, and the west sub sag in northeast sag is the optimum hydrocarbon-generating sag. The method of seismic attribution has been proved to be a feasible and effective way for quantitative prediction on the thickness of source rocks in new exploration areas, and it also can be introduced to areas with simi-lar petroleum exploration conditions.