With the rapid development of micro/nanodevices, it is critical to investigate and disclose the nano-sized tribological properties and deformation mechanisms. This paper aimed to understand nano-tribological behaviours and deformation process of Cu-Ni alloy. The effects of the pressed depth, alloy composition, and sliding distance on friction state, dislocation density, and von-Mises strain stress (VMSS) are comprehensively investigated using molecular dynamics simulation. The results indicate that a larger pressed depth brings about more lattice defects in the pressed region and a higher transverse force, the stacking fault and dislocation density increased rapidly as the Cu content increases, and a longer sliding distance results in more plastic deformation and the number of wear atoms generated. As the pressed depth and sliding distance rise, the plastic deformation and sub-surface damage are aggravated, however, Cu atoms improve the Cu-Ni alloy resistance of deformation. This work can enrich the understanding on the nano-tribological behaviour and deformation mechanism of Cu-Ni alloy during the ultraprecision process.