Abstract: Sensitivity of the waveguide surface plasmon resonance sensor based on intensity detection method should be improved. Modified long range surface plasmon wave, which is excited by the planar waveguide in the dielectric film-metal film-testing dielectric structure, is studied.Method of ion exchange is used to prepare the planar waveguide whose refractive index can be fitted by the FERMI function.Influences of ion exchange time on the modulus and equivalence refractive index are studied, thus the effective basis for the optimization design of the waveguide is provided. An asymmetry structure of dielectric film-metal film-testing film is excited by planar waveguide, and influences of metal material, the thickness of dielectric film and metal film on the characteristic of long range surface plasmon wave are researched.Experiments are realized to detect the refractive index of solutions.Results show that sensitivity of this method is about 6 times that of traditional surface plasmon resonance sensor's, and has a good linear relationship.