The ball shaper is more and more widely used in the repair of the deformed casing. However, the shaping dimension is often determined by experience during shaping. If the dimension of single shaping is too large, the casing is easily damaged. To this end, firstly, the method of single shaping limit research of casing is given. Secondly, the multi-linear isotropic strengthening model is adopted. Considering the material and contact double nonlinear characteristics of casing, a finite element model(FEM)of rolling shaping reducing deformation casing was established. The solution strategy was given and the rationality of the numerical model was verified by experimental research. Finally, the influence of different shaping dimension on the plastic displacement and stress distribution of the casing was revealed.The single shaping limit of the casing with different axial deformation lengths was researched. The results show that with the increase of the shaping dimension, the maximum equivalent stress of the casing,the plastic displacement and residual stress of the casing are all larger after shaping. As the axial deformation length increases, the single shaping limit has a tendency to decrease.The maximum shaping deformation of the deformed casing cannot exceed 36 mm. The research results can provide theoretical guidance for the onsite construction of rolling shaping deformation casing.