An all-optical modulator based on long-range surface plasmon resonance with metal nano-wires array is proposed. It respected for the Kerr effect to induce refractive index changes and numerically investigated respected for using the finite-difference time-domain simulation. The all-optical modulator is realized with low intensity of pump light. The diameter of metal nano-wire, the thickness of buffer dielectric layer and the intensity of pump light have a significant influence on the reflectance spectra of all-optical modulator. The coupling performance of the all-optical modulator is improved by allocating the parameters of metal nano-wire and buffer dielectric layer reasonably. The results show that the mode coupling ability of the all-optical modulator is optimal when the diameter of metal nano-wire and the thickness of buffer dielectric layer are 40 nm and 1 800 nm, respectively. There is a linear relationship between the change of reflectivity spectrum and pump intensity, which the correlation coefficient is 0.998 1. The reflectance of incident light reaches 0.82 by applying the intensity of pump light as low as 0.5 GW/cm2, which can realize all-optical modulation of optical signal to light very well.