The characteristics of the fluorescence spectra and amplified spontaneous emission (ASE) spectra of the RhB/PMMA and the Rh6G/PMMA films in the quasi-waveguides structure are experimentally measured and theoretically analyzed. By using of the radiation of the continue-wave laser and pulse laser, the fluorescence and ASE of the RhB/PMMA and the Rh6G/PMMA films are realized. It is found that the peaks of the fluorescence and ASE are shifted to longer wavelengths as the increase of the dye-doped concentrations and the film thicknesses. By analogy to the model of laser resonance cavity, the self-absorption effect of doped dyes and the gain amplifications of low-order guided modes transmitted in the dyes-doped films are explained for the quasi-waveguides structures and the relation of the wavelengths of fluorescence peak and ASE peak with the dye-doped concentration are obtained. The results show that the theoretical calculations are consistent with the experimental measurement. It is confirmed that the peak-shifts in the fluorescence spectra and ASE spectra are mainly attributed to the self-absorption effect of dye so that the wavelength of ASE peak can be tuned in wider range by the change of doped dye concentration.