Abstract: Chromophoric dissolved organic matter (CDOM) plays an important role in the biogeochemical cycle of aquatic ecosystems. In recent years, under the dual influence of global warming and human activities, hydrological isolation has occurred in most lakes over the world. However, how hydrological isolation affects variations of CDOM chemistry in large lake systems is still poorly understood. In this study, the water samples in the sub-lakes and main lake of Poyang Lake were collected during the dry season in 2021. Composition characteristics and sources of CDOM in the sub-lakes and main lake of Poyang Lake were analyzed by UV-Vis absorption spectra and 3D fluorescence spectra, combined with parallel factor analysis (PARAFAC). The results showed that: (1) The mean values of dissolved organic carbon (DOC) and absorption coefficient of CDOM at 355 nm in sub-lakes was significantly higher than that in main lake (p<0.001). The results revealed more abundance of organic matter in sub-lakes than that in the main lake. (2) Three fluorescence components were identified by PARAFAC, including two humic-like components (C1, C2) and one protein-like component (C3). The average value of the maximum fluorescence intensity (F_max) of CDOM fluorescence components C1~C3 in Poyang Lake showed that the sub-lakes was higher than the main lake. The contribution rates to the total fluorescence intensity of humic-like components (C1+C2) in sub-lakes and main lake were 71.96% and 59.93%, respectively. The proportion of protein fluorescence component C3 in CDOM in main lake was higher than that in sub-lakes. (3) Through the analysis of the characteristic parameters of CDOM in the sub-lakes and main lake showed that the relative molecular weight and humic degrees of CDOM in the sub-lakes were higher than those in main lake. The results of the study contribute to enhance the understanding of the biogeochemical cycle of dissolved organic matter in Poyang Lake and provide scientific references for the management of water environment in large freshwater lakes.