Abstract: Given structured quadrilateral meshes on a certain tool surface, a method of mesh merging to get local coarse meshes of tool surface is introduced such that the simulation model could be simplified and simulation time reduced. This method first searches the original meshes for domain satisfying certain curvature criterion, then checks the boundary types of the original domain. Finally the mesh merging is carried out. Numerical results show this method can not only reduce the simulation time but also keep the simulation accuracy. In fact, this approach can also be used for mesh coarsening of arbitrary surface.