With the long-term exploitation of oil and gas wells, the release of formation pressure leads to changes in formation stress, causing a series of casing deformation problems such as localized depression, shrinkage, and elliptical deformation. These issues seriously affect oil and gas production and result in significant economic losses. To address this, an expansion-type casing shaper has been designed. This tool efficiently converts axial force into radial expansion force to repair deformed casings. However, casing rebound is inevitable during the shaping and repair process, and the rebound amount cannot be directly measured by the tool. To evaluate the effectiveness of the tool in repairing deformed casings and to study the rebound characteristics, a finite element model of the expansion-type casing shaping and repair process was established in Abaqus software. Using a Q125 steel grade, Ф139.7 mm × 12.7 mm (5 1/2″) casing as an example, the repair amount and rebound amount of the deformed casing were quantitatively analyzed. The results show that when the expansion-type shaper applies a maximum axial force of 30 t three times, the tool can pass through the narrowest diameter, expanding the deformed casing from 98.26 mm to 105.72 mm. The error between the experimental data and the model is only 8%, indicating an ideal shaping effect. The established model can accurately simulate the repair and rebound process of casing shaping, providing a theoretical basis for optimizing the tool’s structure and designing process parameters. This research has significant engineering guidance value for improving the efficiency of oil and gas well repair.