During the fabrication of metal/polymer bilayer gratings by nanoimprint lithography, adhesion and friction forces at the interfaces can deform and damage the transferred pattern of the bilayer grating during the demoulding process. To improve the quality of bilayer gratings, the effects of the aspect ratio and metal layer thickness on deformation and stress during the demoulding process in the nanoimprinting of bilayer gratings were investigated. This information was used to determine the optimal grating parameters. The results for the von Mises stress and deformation of bilayer gratings are discussed in detail. The effects of the aspect ratio and metal layer thickness on the grating quality are then considered.