On the basis of detailed lithofacies study, the Longmaxi Formation of Lower Silurian in the MiddleUpper Yangtze is divided into two thirdorder sequences with complete transgression and regression, namely SQ1SQ2, with an average delay of 2.5 Ma. There are mainly seven types of micronano scale microscopic space in the Longmaxi Formation shale reservoir, and fracture reservoir space includes structural shear fracture and foliation fracture. The analysis of relationship between pore volume of different pore size and organic carbon content and methane adsorption capacity of shale indicates that the pore development of shale reservoir was mainly controlled by its organic carbon content. The development of organic rich shales was controlled by organic matter productivity, its accumulation and preservation. The δ13C org near the most flooded surface ranges from -31‰~-30‰, and the content of highly active iron ranges from 1. 0%~1. 56%. The negative drift of δ13 C org and the content of highly active iron are the largest, indicating highest paleoproductivity. The deposition rate is about 7. 5 m/Ma near the most flooded surface. The lower deposition rate is favorable for the accumulation of organic carbon, and the content of organic carbon is as high as 2%~6% in shale.The Th/U ratio is generally 0. 24~0. 54, and V/Cr ratio is 5. 26~8. 27 near the most flooded surface indicating a strong anoxic reducing environment that is conducive to the preservation of organic matter. Therefore, the section of organic rich shale near the most flooded surfaceis favorable for shale gas exploration.