The evolution of micro-voids under dynamic loading mainly contributes to the dynamic damage of ductile materials. In this work, the evolution of a preexisting nano-void in single crystal copper is investigated by means of molecular dynamics(MD) simulation. The relation between the time evolution of complicated stress distribution and the void growth is obtained. The precompression process before the tension process has strong influence to the void growth. That high threshold makes the void grow coincides with the trend that a shorter tension duration wi ll lead to a higher spallation strength, which was found in latest single crysta l spallation experiment.