Abstract: Combined with data of organic geochemistry. this paper is carried out a detailed study on hydrocarbon sourse rocks (coal and mudstone) samples from Xihu sag, East China Sea Basin, mainly through the analystical method of organic petrology. The results demonstrate that source rocks of Xihu sag contain rich vitrinite (> 60%), poor inertinite (<10%) and a certain quantity of exinite plus sapropelinite (10%~30%). Exinite plus sapropelinite content has a close correlation to the yield of choloroform bitumen, total hydrocarbon content and pyrolytic effective carbon amount. Resinite and sporinite plus alginite are the important hydrogen-rich maceral for early and late oil generation, espectively. Based on these, a kind of hydrocarbon generation model is preliminary proposed.