To achieve the thermal stresses analysis of complicated castings, a method of transferring the finite difference meshes into finite element meshes was presented. Furthermore, the stress analysis was carried out by FDM/FEM integrated system. The stress frame specimens were used to validate the method by the comparison of the calculated results based on finite difference meshes with those results based on traditional finite element meshes. It shows the new method is good for the thermal stresses analysis of complicated castings.