The optical third-order nonlinear enhancement factors of gold nano-rings with different thickness of ring walls have been calculated by using the boundary elements method

based on the principle of nonlinear optics and the theory of interaction between metal particles and electromagnetic field.It is shown from the calculation results that with the decreasing of the thickness of the ring walls（d/a from 1 to 0）

the wavelength of gold nano-ring’s surface plasma resonance gets red shift from about 684 nm gradually.However

the third-order optical nonlinear enhancement factor increases to the maximum when d/a at about 0.2 and then decreases during the decreasing of the ring walls’ thicknesses.Devices with relatively strong nonlinear optical effect can be made basing on such property of gold nanorings.