Abstract: Three source rock intervals from the Baiyun Sag are analyzed with geochemical and other techniques, such as rock pyrolysis, kerogen maceral, GC-MS as well as sporopollen and algae analysis, in order to characterize the abundance and types of organic matter. It is revealed that the organic matter mainly comes from higher terrestrial plants and the abundance of the organic matter varies widely. The types of source rocks are closely related to the sedimentary facies or the environment of deposition. The source rock with high abundance and higher plant-dominated organic matter indicates a facies of delta plain; the source rock with moderate abundance and higher plant-dominated organic matter suggests a facies of delta front; the source rock with moderate abundance and mixed organic matter of higher plant and algae indicates a facies of shallow sea, and the source rock with low abundance of organic matter dominated by higher plant indicate a facies of deep sea.