Abstract: In February (dry season) and July (wet season) 2018, the spectral absorption and three-dimensional fluorescence spectrometry analysis of chromophoric dissolved organic matter (CDOM) in Lake Fuxian and its inflowing rivers have been performed to clarify the CDOM’s sources, composition and their spatiotemporal characteristics.The values of a(254) ranged from 3.58 to 4.66 m-1, indicatinglow CDOM abundance. The fluorescence index FI (1.51-1.89), biological autochthonous index BIX (0.81-1.24), freshness index β/α (0.76-1.14) and the humification index HIX (all less than 4 except for HD7 and HD13 during thewet season) of Lake Fuxian and its inflowing rivers,indicated that the CDOMwas mainly autochthonous with a low degree of humification.Five CDOM components were identified by using the parallel factor analysis, including two humus-like components (C1, C2), two tyrosine-like components (C3, C4) and one tryptophan-like component (C5). The CDOM of the inflowing rivers, nearshore and offshore areas of Lake Fuxian during the dry season showed tyrosine-like fluorescence characteristics. However, the CDOM of the inflowing rivers during thewet season showed humus-like fluorescence characteristics.During the dry season, the autochthonous components and their proportion (C3+C4) of Lake Fuxian had larger values. However, in wet season, the allochthonous components (C1+C2+C5) and the HIX were larger. These results indicated the sources of CDOM transformed to allochthonous during the wet seasons. River inputs had few direct contributions on the CDOM abundances of the lake. Due to the strong light radiation, large water storage, long hydraulic retention time and its secondary effects (e.g., microbial actions), CDOM autochthonous components of Lake Fuxian was still up to 45% in the wet season. Furthermore, the varies of BIX、β/α、M in different areas of Lake Fuxian implied that the influences of seasonality on CDOM had spatial heterogeneity.