•Sliding of grain boundary and grain growth play a key role in the plastic deformation mechanism.•Atoms in a state of high stress-strain are located around the abrasive tip and in the grain boundary.•The reverse Hall-Petch relationship is observed within the grain size range of this study.•The ability to lose the material volume of a polycrystalline is larger than a single-crystalline. The mechanical response of CuAlNi nanocrystalline under the nanoscratch through an abrasive tip sliding on the workpiece is investigated using molecular dynamics (MD) simulation. The influences of the grain size, alloy composition, temperature and scratch speed on the plastic deformation characteristic and wear mechanism are surveyed. The results represent that increasing the grain size leads to higher force and hardness, which suggests the reverse Hall-Petch relationship. Meanwhile, the indentation and scratch forces tend to increase when reducing the Cu content and temperature, increasing the scratch speed. The deformation behavior exhibits that grain boundaries play a key role in inhibiting the spread of strain and stress. The results show that the stress and strain are concentrated not only in the contact region between the abrasive tip and substrate but also in the grain boundary and adjacent grain boundary areas. Notably, the sliding, twisting of grain boundary and the fusion of grains are a significant mechanism in the deformation behavior of polycrystalline, resulting in the dislocation is strongly developed in the grain boundary. Furthermore, the movement of atoms in various directions leads to different morphology of pile-up. From quantitative results of the special wear rate show that the ability to lose material volume is larger with Cu86Al11Ni3 alloy and at a temperature of 600 K, as well as the polycrystalline is higher than the single-crystalline. Finally, the residual depth ratios exhibit more strain recovery at the grain size of 6.17 nm and lower temperature. The figure shows the workpiece model (a) and the evolution of grain of CuAlNi alloy at different positions: (b1) before scratching, (b2) an indentation depth of 2.0 nm, (b3) a scratching distance of 1.0 nm, (b4) a scratching distance of 4.0 nm, (b5) a scratching distance of 8.0 nm. Display omitted