In order to improve the surface quality of single-point diamond cutting single-crystal germanium, the orthogonal experiment of three factors and four levels is carried out, and the effect of cutting parameters on the surface roughness under the condition of uneven surface quality distribution of single-crystal germanium is studied by variance analysis and range analysis. The test results show that the contribution rate is the highest when the spindle speed has obvious influence on the surface roughness value, indicating that the larger the spindle speed is, the smaller the surface roughness value is. As a result, an optimal combination of the cutting parameters obtained is that a spindle speed of 3800 r/min, feed rate of 2 mm/min, and maximum cutting depth of 5 μm. Under this cutting condition, high-precision single-crystal germanium with a surface roughness of 2.4 nm is obtained. Next, the surface quality is good and the surface is relatively smooth according to the scanning electron microscope. The chips during cutting are banded, and the material is removed in the plastic range.