In order to investigate the ultra precision cutting characteristics of monocrystalline silicon, nanoindentation and nanoscratch experiments were conducted on <100> surface of monocrystalline silicon using a nanoindentation instrument and a Berkovich diamond indenter. In the nanoindentation experiment, the indenter was pressed onto the surface of monocrystalline silicon under 10, 30, and 50 mN loads, respectively. It is found that there are slight fluctuations in the load displacement curve under 30 mN load, while a "pop out" phenomenon occurred under 50 mN load, indicating a sudden stress change and brittle failure of the material, the critical load for brittle-plastic transition of monocrystalline silicon was predicted to be slightly less than 30 mN. Nanoscratch experiments with variable loads from 0 to 100 mN were carried out. According to the load-displacement curve, it is observed that monocrystalline silicon scratching can be divided into elastic-plastic removal and brittle removal stages during variable load. In the elastic-plastic removal stage, the load-displacement curve fluctuates smoothly, while in the brittle removal stage, the curve fluctuates significantly. The critical load for the brittle-plastic transition of monocrystalline silicon is 27 mN, and the critical depth is 392 nm. Finally, through the constant load nanoscratch experiment, the surface of monocrystalline silicon was scratched at a constant load of 5, 10, and 20 mN in the plastic processing region, respectively. The surface morphology of monocrystalline silicon after constant load scratch was observed by scanning electron microscopy (SEM). The scratching analysis data shows that the cutting force and elastic recovery rate increases with the increase of load, while the friction coefficient first increases and then decreases. Therefore, in ultra precision machining of monocrystalline silicon, it is necessary to select a reasonable machining load and fully consider the impact of elastic recovery.