Abstract: Taking the water source of Z City in winter as the research object, the relationship between the fluorescence composition, source, composition, humification degree of dissolved organic matter (DOM) and the generation potential of trihalomethanes (THMs) was investigated by the combined use of 3D fluorescence spectroscopy, resin separation and classification, and UV-vis spectrophotometry. The results showed that a total of three fluorescence peaks were resolved by 3D fluorescence spectra: protein-like material (C1), ultraviolet humic acid material (C2) and terrestrial/artificial humic material (C3) in the raw water of the water source. The three fluorescence peaks in Q River and X River were 4.50, 10.75, 7.56 and 1.33, 9.24, 7.56, respectively. The fluorescence source index (FI) and biogenic index (BIX) both reflected that DOM of the water source was mainly terrestrial source input. In addition, after the chemical classification of DOM of the water source, the concentrations of five components were as follows: hydrophobic organic acids (HoA) > hydrophilic substances (HiM) > hydrophobic neutral organic substances (HoN) > hydrophobic alkaline organic substances (HoB) > weak hydrophobic acidic organic substances (wHoA). CHCl ₃, CHClBr₂ and CHBrCl₂ were produced by chlorination of Q River raw water, and CHCl₃ and CHBrCl₂ were produced by chlorination of X River, indicating that the river water was not significantly polluted by industry. At the same time, the study of disinfection by-product THMs generation potential was conducted on each chemically graded component of DOM of the water source, and it was found that the main precursors of THMs were HoA and HiM, and HoA, HiM and wHoA had a strong ability to generate THMs, which was consistent with SUVA values of UV absorption characteristics, indicating that the ability to generate THMs was also strong. The industrial polyaluminium chloride should be selected to enhance coagulation for removal.