Three dimension indenter model was established to replace the ideal shape indenter model in the study of nano-indentation simulation. The limitation of short of comparing to actual condition can be solved. Single crystal aluminum surface nano-indentation on the condition of arc indenter is researched by molecular dynamic simulation. The influences of different arc radius of indenter head to testing results are discussed and compared to experiment results. The results show that The measured hardness value increases with indenter head arc radius on the same indentation depth condition. With the increase of indentation depth, the difference between measured results with changed indenter head arc radius reduces gradually. When the indentation depth increase to a certain value, the arc effect of indenter head could be ignored, the measurement will be invariable.