Atmospheric pressure plasma polishing (APPP) is a precision machining technology used for manufacturing high quality optical surfaces. The changes of surface modulus and hardness after machining prove the distinct improvement of surface mechanical properties. The demonstrated decrease of surface residual stresses testifies the removal of the former deformation layer. And the surface topographies under atomic force microscope (AFM) and scanning electron microscope (SEM) indicate obvious amelioration of the surface status, showing that the 0.926-nm average surface roughness has been achieved.