Based on the experiment of fluorescence spectra of thioredoxin reductase (TrxR) from human brain by the excitation of ultraviolet light (UV-light), this paper studies the spectral characteristics and their origins. The experimental results show that, under the excitation of UV-light, TrxR solution emits spectra of region from 280 nm to 720 nm, including two wider bands and many sharper peaks. The wider bands and the sharper peaks represent different tendency along with the change of solution concentration. According to the theory of conversion of internal energy and resonant Raman scattering, the theoretical analyses of TrxR fluorescence spectra are educed. The results indicate that the wide band with the peak locating at 336 nm is the fluorescence from tryptophan in TrxR and the sharper peaks mostly come from the resonant Raman scattering of TrxR. These researches on the emission spectra of TrxR solution may represent an effort to better understand the conformation, structure and vibration of TrxR molecule.