Abstract: Lithofacies control the hydrocarbon generation potential, reservoir property and fracturability of shales. Based on core observations, comprehensively using the techniques such as rock thin sections identification, X-ray diffraction mineral analysis, field emission scanning electron microscopy (FE-SEM) imaging, X-ray fluorescence (XRF) element scanning and major element and microelement testing, the study systematically investigates the shale lithofacies of the upper layer series of development in the first submember of Member 1 of Longmaxi Formation (Long1 Member) in Luzhou area of Sichuan Basin. The results show that the study area mainly develops six lithofacies, i.e., high TOC siliceous shale (S1), high TOC siliceous clay mixed shale (CM1), medium TOC siliceous mud shale (S2), medium TOC siliceous clay mixed shale (CM2), medium TOC mixed shale (M2) and low TOC siliceous clay mixed shale (CM3). Among them, S1 and CM1 are the sweet spot lithofacies of the upper layers in the first submember of Long1 Member. S1 lithofacies is mainly developed at the bottom of the fourth layer and the lower part of the sixth layer in the first submember of Long1 Member, characterized with high organic matter, developed organic matter pores and microcracks, high content of brittle minerals, and the highest gas content, which is classified as the optimal lithofacies type. CM1 lithofacies is mainly developed in the middle and lower parts of the sixth layer in the first submember of Long1 Member, characterized with high organic matter, well-developed intergranular pores of clay minerals, organic matter pores and microcracks, as well as high gas content, which is classified as the suboptimal lithofacies type. The formation of sweet spot lithofacies is jointly controlled by sea level changes, volcanism and upwelling ocean currents. Ce anomalies indicate that a slight rise in sea level causes a decrease in dissolved oxygen concentration in the bottom water. Meanwhile, volcanic ashes release a lot of nutrient elements, and the upwelling ocean currents can provide eutrophic water bodies, thus promoting the marine biological productivity in surface sea water, and forming a set of organic-rich siliceous shale and siliceous clay mixed shale. Moreover, a large number of micro pores and micro cracks were developed during the diagenesis process of the shales.