Abstract: In order to explore the main reasons for water quality fluctuation in the Yixun River in the spring flood season, Yixun River Basin was sampled and investigated in December 2020 and March 2021, respectively. Based on an analysis of the spatial and temporal characteristics of water environment factors, the excitation-emission matrix spectroscopy combined with parallel factor analysis (EEM-PARAFAC), fluorescence characteristic analysis and Spearman rank correlation analysis were used in fluorescence characteristics studies and source characteristics studies. The results showed that the water quality of the Yixun River in the spring flood season deteriorated significantly, which was mainly reflected in the increase in the proportion of Class V and worse water bodies of the national standard from 14.29% to 88.24%. The main over-standard factors were COD_Cr, TP and COD_Mn. Three fluorescence components, including UVC humic-like substances (C1), UVA humic-like substances (C2), and tryptophan-like substances (C3) were detected in the dissolved organic matter (DOM) in the water body, of which the total contribution of humic-like substances accounted for nearly 80%. The fluorescence index (FI) of DOM during the freezing and spring flood seasons were 1.65-1.88 and 1.49-1.75, the biological source index (BIX) was 0.76-1.31 and 0.65-0.99, and the humification index (HIX) was 0.10-7.00 and 0.40-6.00, respectively. During the spring flood season, the DOM of the Yixun River body showed stronger humility and weaker recent autochthonous characteristics, and the proportion of land source contribution significantly increased. The fluorescence parameters of FI and BIX were significantly negatively correlated (R>0.6, P<0.01) with the water quality parameters such as DOC, TP, COD_Cr and COD_Mn. The increase of the concentration of DOC, TP and other pollutants in water bodies during the spring flood season was mainly affected by three factors, including high humus background, soil erosion and agricultural non-point source pollution.