The marine shale gas reservoirs bring great challenges in reservoir characterization due to complex depositional and diagenetic processes, and fine grain and much smaller pore size (from nanometer to micrometer). Reservoir characteristics of marine gas shales are considered as a key factor affecting the enrichment and resource abundance of shale gas. Recently, significant understanding have been achieved in organic matter characteristics, petrology, lithofacies, diagenesis, porosity and permeability, pore structure characterization and mechanical properties with the application of advanced techniques. Organic matter in shales is considered to be closely related to its maturity. The determination model of rock mineral components has been attempted to build quantitatively. The lithofacies prediction and 3D modeling techniques can be applied in shales. The diagenetic effects on shale reservoirs are required to be further explored. The understanding of the trend of porosity and permeability is still a challenge to be identified. The pore structure has recently allowed better characterization from qualitative to quantitative. The analysis of the mechanical properties of shales will help to guide the hydraulic fracturing strategies. Furthermore, the research trends and the development directions should be closely combined with the systematic characterization of pore architecture and networks in gas shales, and with the temporal and spatial configuration of diagenesis and lithofacies in regional scale, together with the intrinsic connections among diagenetic evolution, lithofacies, pore system, and organic matter abundances.