This study focuses on the composition and sources of dissolved organic matter (DOM) in the Fancun Reservoir, located in Ningguo City, Anhui Province, China. The investigation was conducted by analyzing the spectral characteristics of DOM using UV-Vis absorption spectra and fluorescence spectroscopy. The humic substances were dominated by fulvic acid, with an average DOM concentration of 30.54 mg/L at the reservoir outlet primarily originating from internal release. Fluorescence indices suggested a strong autochthonous contribution of DOM and weak humus characteristics. Three DOM components were identified through parallel factor analysis. Aromatic protein substances in DOM ranged from 0.52 to 4.49%, suggesting minimal anthropogenic influence. The average fluorescence lifetime increased from 0.81 ns at the reservoir entrance to 0.91 ns at the outlet, with an average relative quantum yield of 4.99%, implying stabilization throughout the reservoir. Correlation analysis indicated positive correlations (P <
0.001) between absorption coefficients at specific wavelengths. Principal component analysis explained 67.7% of the total variance, indicating highly common DOM sources across sites.