Parallel factor analysis method was used to analyze the three-dimensional fluorescence spectra of dissolved organic matter in the water of Taihu Lake. Based on analysis of the error squared sum of excitation and emission wavelength, the core consistency and the simulation of three dimensional fluorescence spectrum and residual spectrum when the factor of the PARAFAC model is 3, 4 and 5, results show that the best factor number of parallel factor model was three. The three fluorescence components were identified, including humic-like component, tryptophan-like component and tyrosine-like component.