In the present technology, the manufacture of micro-electro-mechanical system (MEMS) and nano-electro-mechanical system (NEMS) are limited by the lack of mechanism of material processing, especially the mechanism of the polycrystalline materials. In this work, based on the microstructures of polycrystalline copper, the evolution mechanism of dislocations on the polycrystalline copper nanoindentation surface is researched by the four types of microstructures in polycrystalline materials, including grain cell, grain boundary, triple junction and vertex points. In addition, the coordination number, internal stress and atomic potential energy of the dislocations defects are also considered. The results show that when the microstructures with high dimension number carry the compressive stress, the adjacent microstructures with low dimension number appear tensile stress and the microstructures with lower dimension number like vertex points is more likely to appear tensile stress. The dislocation atoms accumulate high internal stress and atomic potential energy during the dislocation nucleation. The internal stress of the imperfect dislocation atoms at the dislocation edge is higher than that of the stacking layer atoms inside the dislocations during the dislocation growth. The process of nucleation and growth, and the internal stress accumulation and release both have similar directionality. They both firstly extended to the microstructures with lower dimension number like vertex points and triple junction, and then expend to and stop at the grain boundary with high dimension number.