Cu nanowires covered by Ag particles is studied for potential applications in the next-generation microelectronics. To date, the deformation mechanism in the CuAg core-particle is not clear. Here, molecular dynamics simulation is used to describe the CuAg core-particle system. The results show that the equilibrium structure of Ag particles is reconstructed, when the particle ≤1.0 nm. At low temperature (1 K) indicate that three different deformation processes take part in the core-particle structure, depending on the size of Ag particles. When the particle diameter ≤2.0 nm, the prevailing deformation mechanism is the emission of dislocations from the Cu surface. For the particle diameters ranging from 3.0 to 6.0 nm, the emission of misfit dislocations from the AgCu interface is the dominant deformation mechanism. If the Ag particle ≥6.0 nm, the deformation mechanism can be characterized by the slip band, consisting of the dislocations and amorphous atoms. For elevated temperatures (2–400 K), the mechanical properties of the AgCu core-shell system are nearly independent of temperature, whereas the structure with particles larger than 2.0 nm showed a strong dependence of its mechanical properties on temperature. Based on the results, the diameter-temperature plastic deformation map is proposed.