The small polaron Nb4+Li fluorescence spectrum is in the range of 700—950 nm. Researches of the pure lithium niobate samples with the same composition and different reduction degrees show that the intensity of the fluorescence spectrum reflects the chemical reduction degree of the material. From the shallow level of small polaron, we propose a model of “one center and three energy level” to explain the process of polaron fluorescence. For titanium-diffused lithium niobate (Ti：LiNbO3), homogeneity of the chemical reduction level would be destroyed during fabrication. From the scans of Ti：LiNbO3 waveguide sample, the intensities of fluorescence spectrum on the surface and in the bulk, as well as inside the waveguide and outside the waveguide, are evidently different (intensity on the surface is 6—8 times of that in the bulk). Our researches indicate, using the non-destructive technology of polaron fluorescence spectrum is effective to control the necessary heat treatment in the waveguide fabrication processes. At the same time, the difference in intensity reflects indirectly the profile of the waveguide.