Abstract: To understand the influence of crystal directions on manufactured surface roughness of different crystal silicons in ultra-precision turning clearly and find the optimal cutting directions, a novel approach to analyze surface roughness using surface roughness distributions and Euclidean Distance was provided in this paper. There are several steps to conduct to study the surface roughness as follows in this paper. Firstly, the surface roughness of a monocrystalline silicon wafer was manufactured by a single point diamond cutting tool with different cutting parameters in different cutting areas. Then the values of surface roughness of the silicon wafer were obtained using a white light interferometer Talysurf CCI 6000. After that, the measured surface roughness data were pretreated with boxplots analysis, in order to find and get rid of the influence of the outliers. Finally, the roughness values along different crystal orientations of the manufactured wafer were analyzed using mean roughness value analysis and Euclidean Distance table. It shows that the crystal orientations and cutting parameters have much influence on surface roughness.