Based on the analysis of the regional geological setting of the Central Hunan depression and the Southeast Hunan depression and the geological characteristics of the marine shale and using outcrop observations, drilling data, experimental testing and other methods, the authors study 24 shale samples from 7 targeted layers of Devonian-Permian, make the mineral X-ray diffraction quantitative analysis, field emission scanning electron microscopy, and isothermal adsorption simulation experiments, and emphatically analyze the degree of the influence of the organic geochemical parameters, mineral composition and microcosmic pore structure on the gas-bearing characteristics. The results show that the spaces of the occurrence and adsorption of the shale gas are mainly grid holes, corrosion holes, organic holes, organism cavities and micro-fractures. The adsorbed gas content averages over 1. 51--1. 60 cm3/g. The main influential factors that affect the adsorbed gas content are organic carbon content, clay mineral content, maturity of organic matters, pore size and specific surface area.