In order to improve the surface quality of ultra-precision machining of aluminum mirror,the surface quality evaluation method of ultra-precision cutting and the factors affecting the surface quality were introduced,the influence mechanism of each factor on the surface quality was analyzed.The single variable method was used to carry out the single-point diamond turning experiment of Al6061 with different process parameters,through the comparison of surface roughness and power spectral density,the influence of each process parameter on the surface quality was studied,and the optimal process parameters were obtained; the optical surface with surface roughness of 4.67 nm was finally processed.