In this paper, a remesh-free deformation method is proposed to speedup the modeling of electric motor in the optimal design process. In the proposed method, neither mesh regeneration nor an increase in the number of unknowns is required. By defining the boundary mesh as well as the fine computational mesh, refined meshes can be quickly derived using a coordinate mapping technique. The calculation time can, therefore, be greatly reduced when the geometric parameters are changed according to the optimal design. At the same time, the mesh quality is guaranteed to ensure an accurate requirement of the finite-element method. Numerical examples, both in, 2-D problems and 3-D problems are reported to demonstrate the efficiency and effectiveness of the proposed method.