The dispersion relation for coaxial dielectric-metal-dielectric structure by making an explicit connection with the planar dielectric-metal-dielectric structure is obtained. Each mode splits into a high effective refractive index branch and a low effective refractive index branch. An intuitive picture that allows for a qualitative understanding is provided. The effective refractive indexes and propagation losses of the modes are calculated by using the analytical dispersion expression. They fit well with the numerical simulation results obtained by using finite element method in the range of 0.5~1.5 μm. The results the applicability of the dispersion equation are also analyed.