The lithofacies study of finegrained sedimentary rocks is an important foundation for better understanding hydrocarbon source rocks and tight oil and shale oil reservoirs. Considering the variety of downfaulted basin environments, multiple types of fine grained sediments and complex of rock assemblages in China, it is highly necessary to carry out lithofacies classification for finegrained sedimentary rocks. Paleogene finegrained sedimentary rocks in Bohai Bay Basin was taken as a study objective to probe the basic features of finegrained sedimentary rocks through description of centimeterlevel cores, identification of thin sections using a confocal laser scanning microscope, and analysis of whole rock Xray diffraction. Lithofacies of finegrained sedimentary rocks in continental faulted basin can be classified based on the following (1) vertical rock assemblage types summarized by detailed description of core; (2) analysis of sedimentary microenvironment; (3) rock types and lithofacies grouping of different rock assemblage types using whole rock Xray diffraction and scanning electron microscopy technology; (4) superimposition relation under microscope; and (5) genesis and forming mechanism of lithofacies. Our classification for lithofacies can meet oilfield prospecting requirements that are easy to conduct facies classification and establish the relation between rock types and logging data. And subgroup classification can also facilitate analyses of the relation between source rock and reservoir, microenvironment of sedimentation, and microscopic structure of reservoirs.