Abstract: Based on the electromagnetic scattering theory and the equivalent principle for the electromagnetic scattering, we transform the metallic nanosphere particle with the permittivity properties including spatial dispersion （or nonlocal effect） into that in the local case without spatial dispersion, and further obtain the equivalent permittivity and permeability for the metallic nanosphere particle with spatial dispersion. Finally, with a concrete example, it is found that because of the existence of the longitudinal mode field inside the metallic nanosphere particle, there are the differences for the electromagnetic parameters between both above cases, which is especially obvious in the low-frequency region.

Key words: equivalent permittivity, equivalent permeability, nonlocal, Mie theory, scattering cross section