Fluorescence spectra and fluorescence quantum yield of triton X-100 (TX) aqueous solution are reported. In strong acidic solutions, TX gives no fluorescence. When pH > 1, TX gives a strong and steady fluorescence with the maximum excitation wavelengths at 229 and 275 nm, and the maximum emission wavelength at 302 nm, respectively. TX aqueous solution can produce resonance fluorescence. The resonance fluorescence peak is located at 285 nm. A linear relationship between the fluorescence intensity and TX concentration was found in the range of 0. 1-90 mg x L(-1). The detection limit of TX is 0.1 mg x L(-1). By using L-tryptophan as a reference, the fluorescence quantum yield of TX at maximum excitation wavelength 280 nm was measured to be 0.121.