In this article, based on the method of molecular dynamics, the mechanics response of nano-component is simulated. Some details of MD technique have been included in this paper, dealing with time step, algorithm and other problems. According to the work of predecessors, systemically a general form of atomic stress under atomic scale, as well as its specific form using EAM method, is derived. Unlike the macro stress, the atomic stress stands for the atom’s potential ability of movement, and should be defined again. The mechanical properties of copper nano-rod are studied, including relaxation state, tensile state and compress state. Because of the high energy atoms on the surface, the surface effect is generated. So when in relaxation state, the nano-rod will be shortened, and the more atoms the rod has, the less is shortened. When the strain is between –0.1 and 0.1, the nano-rod performs elastic situation. The nano-rod has a highly tensile strength. We find that dislocation can reduced the flow stress of the nano-rod. Finally the effect of nano-hole effect is discussed.