This work presents a comparison of numerical simulation and experiment of nanoindentation testing. A commercial finite element code ANSYS is adopted in the numerical simulation, in which elastic-plastic properties are considered. A PMMA specimen and a three side pyramidal Berkovich probe tip is used in the indentation tests. While the elastic-linear workhardening properties are adopted, the numerical results agree well with the experimental data for different indentation loads. It proves the numerical simulation can be used in the small scale analysis.