Through molecular dynamics simulations,the mechanical behavior of nanoporous copper under impact loading was investigated with relative densities ranging from 77.91% to 98.36%,focusing on deformation mechanism,the scaling laws and influence of ligament sizes.Results show that the classical Gibson-Ashby′s scaling laws should be modified for prediction of both the Young′s modulus and yield stress.A proportional relationship is established between cell wall thickness and yield stress,and new modified scaling equations are built for nanoporous copper with consideration on both relative mass density and size effects of ligaments.The size effect can be explained by larger surface area/volume ratio of samples with thinner ligament size and limited dislocation source activation due to narrow space between larger numbers of voids. Through molecular dynamics simulations, the mechanical behavior of nanoporous copper under impact loading was investigated with relative densities ranging from 77.91% to 98.36%, focusing on deformation mechanism, the scaling laws and influence of ligament sizes. Results show that the classical Gibson-Ashby ’ s scaling laws should be modified for both of Young’s modulus and yield stress. A proportional relationship is established between cell wall thickness and yield stress, and new modified scaling equations are built for nanoporous copper with consideration on both relative mass density and size effects of ligaments. The size effect can be explained by larger surface area / volume ratio of samples with thinner ligament size and limited dislocation source activation due to narrow space between larger numbers of voids.