Sustained casing pressure in wells has troubled safety production and environment for decades, a casing pressure prediction model based on the assumption of the casing deformation during the gas migration process. The casing is extruded and annulus is expanded by the gradually increased casing pressure. The coupling change of volume and pressure is calculated by an iterative calculation method that as shown in the calculation procedure. Results show that the major impact of casing deformation is that the required stabilized time is being prolonged. It has no influence on the maximum casing pressure. In the later of gas migration process, buildup curves move to right because the casing deformation provided a more annular space that compared to the assumption of the rigid annular space, the expanded annulus space makes the casing pressure of trapped annular fluid and gas deceased. The calculation results are compared with the published results of the gas well, the illustration well was troubled by sealing failure. The casing pressure buildup curves agree well with the field data. The research has a reference for accurately predicting casing pressure and damage condition of well integrity in the gas wells.

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