In this study, based on results of core observations, thin sections, X- ray diffraction and scanning electron microscopy (SEM), combined with inorganic geochemical indicators,the lithofacies characteristics and sedimentary environment of shallow lacustrine fine- grained rocks in the second Member of Qiketai Formation (J2q2) are studied. The sedimentary genetic model of shallow lacustrine fine- grained rocks was established, and the significance of shale oil/tight oil reservoirs is also analyzed. The results show that the fine- grained sedimentary rocks in the study area have complex mineral composition and sedimentary structure, and the content of organic matter varies greatly.Based on the mineral composition, sedimentary structure and organic matter characteristics, fine- grained rocks of J2q2 were divided into 11 lithofacies types, which were mainly multi- components mixed lithofacies, each of which had a variety of sedimentary structures, including massive, granular and laminated types. Organic matter- bearing massive felsic fine- grained mixed/sedimentary rock lithofacies, organic matter- bearing massive carbonate fine- grained mixed/sedimentary rock lithofacies, and organic matter- bearing massive argillaceous fine- grained mixed/sedimentary rock lithofacies prevail, with a small amount of organic matter- rich laminated carbonate fine- grained mixed/sedimentary rock lithofacies and granular carbonate fine- grain mixed/sedimentary rock lithofacies.Under the conditions of arid paleoclimate, high paleosalinity, relatively deep water column and weak terrigenous clastic supply, chemical and biochemical changes in the water column of lacustrine basin caused development of carbonate fine- grained mixed/sedimentary rocks.The lithofacies in different sedimentary environments frequently overlap and alternate in vertical direction, which can be recognized as four types of lithofacies assemblages. They were formed in shallow carbonate granular beaches- lacustrine bays assemblages, lacustrine bays and lime mud flats assemblages, lime mud and sand- mud flat assemblages, mixed sedimentary beach bar and shallow lake mud assemblages, respectively.Finally, based on the research of the lithofacies types, characteristics, sedimentary environment and vertical evolution sequence of fine- grained rocks, the sedimentary model of the shallow lacustrine fine- grained rocks in the J2q2 was established. The fine- grained rocks have moderately high hydrocarbon generation potential, and the fine- grained rocks with high carbonate content develop carbonate intercrystalline pores and microfractures. Moreover, the fine- grained rocks are suitable for fracturing because of high brittle mineral content. They have favorable conditions for shale oil and tight oil accumulation, and are significant for exploration.