In order to achieve the fine characterization and integrated evaluation of the geological body of the depleted gas reservoir and effectively guide the well location design and optimization of the injectivity and production Wells of the gas reservoir, large-scale structural modeling technology including cap layer, fault, reservoir and floor, sedimentary facies and petrofacies modeling, as well as attribute modeling methods such as porosity, permeability and saturation were adopted in the LN gas reservoir as the research object. The large scale fine 3D geological model of gas reservoir in depleted gas reservoir is established. The results show that the favorable reservoirs of LN gas storage are the sand body of underwater distributary channel, estuary bar and sheet sand. The direct cover layer is the mudstone layer under the HII2 small layer, and the bottom layer is the mudstone layer above the HII4 small layer. The distribution of the cover layer and the bottom layer is stable and the sealing property is good. The reservoir section has good physical property conditions, with porosity ranging from 20 to 25%, permeability ranging from 50 to 200 mD and gas saturation ranging from 50 to 70%.The spatial distribution of gas reservoir geological characteristics and attribute parameters is described by large-scale 3D geological modeling, which provides decision-making basis for gas storage well location deployment and horizontal well drilling trajectory design.