In recent years，the exploration and development of shale gas in Southeast Chongqing has become the focus of oil and gas exploration in China. In this article，the geologic characteristics of shale gas accumulation in Longmaxi Formation in the southeast of Chongqing were systematically analyzed in terms of stratigraphic sedimentation，geochemistry，reservoir characteristics and reservoir pattern. The results show that the shale thickness of the Longmaxi Formation in the southeast of Chongqing is larger，ranging from 30 to 130 m. The sedimentary center，where the organic carbon content of shale is high （about 0.05%-17.4%），is in the Shizhu-Pengshui area，so it is the area with high organic carbon in Pengshui. The type of organic matter is dominated by amorphous sapropelic matter，and the degree of thermal evolution reaches high-over maturity. The mineral composition of the reservoir is complex. The clay minerals are composed of illite，mixed-layer minerals of illite and montmorillonite and chlorite. The brittle minerals include quartz，feldspar and carbonate minerals and the brittleness index is high. The storage space is dominated by organic pores，intergranular pores，intragranular pores，pores between interlayered clay minerals and fractures. Shale gas accumulated in situ to form a gas reservoir，and the gas was mainly generated from crude oil cracking and organic matter pyrolysis.