[Purposes] This paper aims to study the mechanical properties and cutting characteristics of single crystal GaN at the micro-nano scale, which provides theoretical basis and data support for its micro-nano fabrication, and also offers a technical basis for ultra-precision processing of semiconductor hard and brittle materials. [Methods] The mechanical properties of single crystal GaN were studied by nanoindentation. The process of material removal and influence of constant load scratch parameters on the cutting characteristics were also analyzed by nano-scratch test under variable and constant load respectively. [Findings] The average hardness and elastic modulus of single crystal GaN were 6.06 and 92.90 GPa, respectively, and the elastic recovery rate and elastic energy recovery rate decreased with the increasing of pressing load. The critical loads of elastic-plastic transition and brittle-plastic transition were about 390 and 1 200 mN, respectively. The cutting force and friction coefficient increased with the increasing of cutting speed and normal load. [Conclusions] In the normal loading range of 390~1 200 mN, the ductile removal of single crystal GaN can be achieved. The reduction of brittle fracture damage in the process of scratching and improvement of machined surface quality also can be obtained.