Abstract: As the second largest lake in Xinjiang, Ulungur Lake is of great significance in maintaining the ecological balance in the northwest region of China. In order to explore the reasons why the organic indexes of Ulungur Lake exceeded the standard during the ice sealing periods, the dissolved organic matter (DOM) of water body during the ice sealing period was taken as the research object, and the spatial distribution characteristics and source analysis of DOM in Ulungur Lake were discussed by means of ultraviolet-visible absorption spectroscopy and three-dimensional fluorescence spectroscopy combined with parallel factor model (PARAFAC) and correlation analysis. The results showed that the ultraviolet-visible absorption spectrum parameters (E₃/E₄) of DOM in Ulungur Lake during the ice-sealing period were greater than 3.5, indicating that the water humus was mainly fulvic acid. PARAFAC analysis showed that DOM of Ulungur Lake contained three main fluorescent components, namely terrestrial humus (C1, 39.03%), tryptophan-like substance (C2, 38.20%) and fulvic acid substance (C3, 22.77%). The average fluorescence index (FI), humification index (HIX ) and autochthonous index (BIX) of the water body of Ulungur Lake were 1.64, 1.66 and 1.03, respectively. The fluorescence characteristic parameters showed that the DOM of the water body was composed of terrestrial and autochthonous sources, and had the characteristics of low humification and high autochthonous sources, indicating that the DOM of the water body of Ulungur Lake was mainly produced by endogenous sources. Humus (C1, C3) was significantly correlated with protein-like components (C2) (P< 0.01), indicating that the production and source of humus and protein-like components were consistent. The study on the characteristics of DOM in Ulungur Lake during the ice sealing period could provide a theoretical basis for the treatment of organic pollution in Ulungur Lake.