The effect on light transmission characteristics of the dielectric-met al (IM) structure and metal- insulator-metal (MIM) waveguides was compared and analyzed using two-dimension al finite difference time domain(FDTD)method in this paper.The optimal propagation length can be obtaine d after optimizing of structure size and refractive index of IM structure.The numerical results indicate that t he propagation length of surface plasma waveguides with IM structure is longer than that with MIM structure.We al so found that the best propagation result of the IM structure waveguide can be achieved when the medium thickness is 300nm a nd the thickness of the metal layer is 200nm.Based on those parameters,we calculate the effect of refractive index of the dielectric layer.on the optical transmission characteristics of IM waveguide.We find that the propagation length of surface plasma waveguide is longest when refractive index is 1.5.The design and optimiza tion of waveguide structure parameters not only broaden the theoretical basis of the dielectric loaded surfa ce plasmon waveguide structure,but also have potential applications in the research of nano optical integrated devi ces.