The invention relates to a new technology which uses a surface modification method for ultra-precision machining, and in particular relates to a particle beam-assisted ultraprecision machining method for single-crystal brittle materials. The invention, the particle beam-assisted ultra-precision machining method for single-crystal brittle materials, can significantly improve machining accuracy, reduce surface finish and greatly reduce tool wear during ultra-precision machining of brittle materials. The method adopts the technical proposal that the method comprises of the following steps: a) utilizing simulation software to simulate modification parameters according to cutting depth, surface roughness and other machining requirements; b) using particle beams to bombard or irradiate the surface of a single-crystal brittle material to be machined, according to the energy and fluence obtained from the simulation results; c) utilizing ultra-precision cutting (or grinding) technology to perform ultra precise cutting on the single-crystal material which is bombarded or irradiated by the particle beams; and d) measuring and characterizing the surface quality of the machined material and comparing the improvement of the machined surface quality with that of the unmodified machined surface. The method is mainly used for machining the single-crystal brittle materials.