The tensile failure mechanism of Cu-Polyethylene (PE)-Cu (CPC) sandwich structure was clarified by molecular dynamics (MD) simulations subjected to a uniaxial tensile loading at microscopic scale. The sensitivity analysis of parameters such as mixing rules in describing the interaction between the wall (Cu) and the sandwich layer (PE), model size, relaxation time for equilibrium and initial velocity distribution was carried out to verify the rationality of modeling. The evolutions of stress-strain relationship and each potential energy component were provided to describe the failure process of the structure. The peak of non-bond energy shows a delay compared to the yield point in stress-strain curve, which coincides with the local maximum point of the trans-fraction curve of dihedral angles. After that, an inflexion appeared in the trans-fraction curve indicates an energy transport process, which corresponds with the slope change of the stress-strain curve. It is assumed that the dihedral distribution plays a crucial role in the damage process of CPC structure. In addition, the temperature field and the density profile were adopted to predict the position of damage initiation, which was confirmed by the microstructure evolution. The intrinsic thickness-dependence of CPC was explored by taking the coupling effect of bridging and entanglement into account, which is in reverse proportion with the yield strength of CPC.