Abstract: Many Cenozoic sedimentary basins developed in China marginal seas, of which the chief oil source rocks are lacustrine ones developed in rifting Ⅱ phase (developmental phase). Representative source rocks are the third member of Eocene Shahejie Formation in Bohai Sea, the Eocene Liushagang Formation in Beibuwan Basin, the EoceneWenchang Formation in Pearl River Mouth Basin, and the Eocene Yueguifeng Formation in the western depression of East China Sea Basin. Chief gas source rocks of many basins are source rocks in coal measure, which developed in rifting Ⅱ phase (decline phase). The representative source rocks are the Oligocene Yacheng Formation in Qiongdongnan Basin, the Eocene-Oligocene Enping formation in Pearl RiverMouth Basin, and the Eocene Pinghu Formation in eastern depressions of East China Sea Shelf Basin. The formation of high grade source rocks depends on abundant organic matter and paleoenvironment suitable for preservation and transformation of organic deposition. Research on the variations of palynoflora, algae and fragmentary organic matter that have been conserved in strata is an effective channel for investigating the paleoenvironment and distinguishing the growth of high grade source rocks. So, characteristics of paleoecospecies and fragmentary organic matter are feasible paleoecological marker for forecasting the growth of high grade source rocks. To study vertical and horizontal organic facies in suitable strata in combination with the paleoenvironment, paleobiology, and organic geochemistry when organic matter formed is reasonable methology for forecasting the distribution of high grade source rocks

Key words: lacustrine source rocks, coal-measure source rocks, organic matter, paleoenvironment, paleoecospecies, organic facies; rifting phase of basin, China marginal seas