The numerical controlled plastic film cutting machine in our design is used for flower bags making. It is composed of four parts; cutting mechanism, delivering mechanism, tool rest and machine bed. The tool rest is a critical structure to cutting and adhering operations. The tool rest is a long -thin rod with big span, usually it’s failure is because of bending deformation caused by less stiffness. In this study, we finished FEM 3D modeling of tool rest structure to increase its structure stiffness. We analyzed bending deformation characteristics of the tool rest, performed 3D FEM analysis and choose a relatively reliable structure after comparing maximum deformation in three different candidate structures. As a result, support structure of the tools rest was optimized, providing us a numerical data for structure reformation.