Abstract: According to the characteristics of geochemistry, petrology and sedimentology, the paper evaluates the organic matter-rich mudstones in the Paleogene Shahejie formation, Ed3 and the lower Ed2 from organic matter abundance, type and maturity, and analyzes their hydrocarbon potential, repectively. Meanwhile, the paper studies the controls of structural subsidence, sedimentary rate, dilutive effect and sedimentary facies on organic matter abundance. The result shows that the organic matter abundance of Es3 source rocks which is featured with rich algae, rapid subsidence and high ratio of mudstone thickness to gross thickness is relatively high in the southern and middle Liaozhong sag, moderate in the northern sag. The organic matters are mostly Type Ⅱ with large hydrocarbon potential. The source rocks of Es1 and Es2 developed during thermal subsidence stage have high-highest organic matter abundance with the organic matter of Type Ⅰ and Ⅱ, and being low mature-mature. The source rocks of Ed3 which was rapidly deposited during extensional rifting stge have relatively high organic matter abundance in the southern and middle Liaozhong sag, moderate in the northern sag. The organic matters are dominated by TypeⅡ1 and Ⅱ2, being immature-low mature. The dilutive effect of the lower Ed2 is obvious so that the organic matter abundance is not high, indicating the source rocks in the lower Ed2 being immature-low mature