For the first time, we introduced a simple method of synthesizing segregated thin antimony nanowires based on the principle that nanoparticles can spontaneously self-assemble into crystalline nanowires (similar to20 nm) in the absence of any rigid templates at room temperature. By collecting electron energy loss spectra from individual Sb nanowires with different diameters, we investigated the effect of nanowire diameter on plasmon excitations in Sb nanowires. As the diameter of Sb nanowire decreases, we find that the peak energy of surface plasmon shifts toward the lower energy.