The evaluation of fault sealing is important research content in the early evaluation of underground gas storage construction. To accurately predict the pressure limit of the fault, a new method involving the analysis of fault lateral sealing and a comprehensive evaluation of mechanical stability is proposed in this paper. The results show that the Shale Gouge Ratio values of the faults in the reservoir building area are all greater than the critical value, which can ensure the lateral sealing of this area. After reservoir development, pressure failure causes the horizontal principal stress to decrease, but the effective normal stress and shear stress on the cross section increase, the fault stability index increases to 0.8, and the risk of fault reactivation risk increases. The simulation results show that when the pressure decreases to 35.5 MPa or increases to 65.5 MPa, the Fault F1 stability index first approaches the critical value of 1, and the fault appears to fall into slip instability. This study shows that the safe operating pressure range of this reconstructed gas storage reservoir is 35.5~65.5 MPa. The quantitative evaluation results are given in this paper, and it also gives early warning of potential risks.