Ultra deep gas reservoirs are generally characterized by high-pressure or ultra-high pressure, dense matrix and fractures development, which lead to strong stress sensitivity in gas reservoir development. While the physical simulation of high temperature and high pressure gas reservoir is difficult and low reliability. In this paper, the reverse reconstruction technology is used to establish the reservoir fracture grid model. Combined with the parameters of reservoir rock mechanics and high-pressure physical properties of natural gas under formation conditions, the finite element analysis is used to simulate the fracture closure law in the process of gas reservoir development, and then the natural gas seepage simulation is carried out for the fractures with different fracture closure degrees, so as to realize the fracture seepage simulation characterization of high-temperature and high-pressure gas reservoir. The results show that: ① the reservoir of Qixia Formation is mainly fracture pore type reservoir, and the fracture is mainly through fracture and low angle fracture.② In the early stage of fracture closure, some micro convex bodies are basically free of force, and the fracture opening decreases rapidly, and the permeability decreases rapidly; in the late stage of fracture closure, the micro convex bodies is forced to increase, the fracture opening tends to be stable, and the permeability is basically stable.③ The results show that the fracture opening of Qixia Formation is about 0.1 mm, and the fracture is not completely closed; when the fracture pore pressure is less than 60 MPa, the permeability is basically stable.