Monte Carlo method is used to simulate the point source full energy efficiency of the high purity germanium probe on the axial and at the side. By comparison with the results, found that there is a large deviation between experimental data and simulation data. In this study, by continuously adjusting the radius, thickness of the Ge crystal and the thickness of the copper holder, the accurate simulation size is obtained. The result suggests that: Use the adjusted dimensions, the full energy efficiency between simulate and measured results were m...