A set of organic-rich shale formation developed in the Late Ordovician-Early Silurian in Dingshan area，southeastern Sichuan Basin. According to the drilled wells，it is revealed that this area has good shale gas exploration and development prospects. However，the exploration gas test results after fracturing in the exploratory wells differ significantly. The “six properties”，known as the gas reservoir organic geochemistry，the gas-bearing property，the lithology and mineral composition，the brittleness（fractability），the physical properties and the heterogeneity（anisotropy），and the sedimentary environment of the Wufeng-Longmaxi Formation were studied by means of radioactive elements logging，organic geochemistry analysis，core description，whole rock X-ray diffraction，scanning electron microscope，physical property test，field gas content test，etc. The results show that the shale sedimentary environment of Wufeng-Longmaxi Formation is marine anoxic reduction environment，based on the results of radioactive elements（Th/U<7，V/Ni>1.0 and V（/ V+Ni）>0.56）. From the top to the bottom，the shale lithology changes from gray black silty limestone and clay to black anoxic shale that is rich in carbonaceous and graptolite，accompanied with an increasing trend in brittle mineral content，TOC，Ro and gas content. At the bottom of the target shale layer，the brittleness index is higher than 50%；the TOC is larger than 2%；the Ro is higher than 2%，the gas content is more than 3 m3/t；and the organic matter type is mainly type I kerogen，which is generally in the late mature stage and the post mature stage. The porosity of inorganic matter is generally smaller than that of organic matter，and the vertical permeability is much smaller than the horizontal permeability in different formation conditions. An anoxic and occlusive reduction environment is the basis for the enrichment of organic matter. A good preservation condition is the key to shale gas accumulation.