The testing methods for nanomechanic properties of materials widely used in machining in micro-nano scale,MEMS/NEMS,biomedical engineering,material sciences etc.are researched and the main principle and methods of nanoindentation technology are analyzed.By a four-sided Vickers diamond indenter with a sharpened tip,the nanoindentation experiments are undertaken to test the single crystal silicon on (100) crystal surface with the help of a nanoindentation tester.Experiments show that the brittle crack is occurred around the nanoindentation zone on silicon surface when the maximum load of indentation is 1 000 mN.However,the crystal silicon shows plastic property when the maximum load of indentation is below 80 mN.Moreover,the hardness test of the crystal silicon with different loads is carried out,and the testing results show that the hardness is quite different in different loads.It is explained that the appeared phenomenon may come from the phase transformation under the nanoindentation zone inside the silicon wafer,because the pressure around the nanoindentation zone is different.The testing result of the hardness of single crystal silicon is about 15.7 GPa.