Most lakes in the Yangtze River Delta are not directly connected to the mainstem of the Yangtze River, and are characterized by low and flat terrain, limited water exchange, long water retention time, and with dense towns and population in the surrounding areas. Therefore, those lakes share distinct sources and optical composition of chromophoric dissolved organic matter (CDOM) and associated driving factors compared with lakes connecting to the mainstem that have short water retention time. In this study, we selected three medium-sized yet important lakes that are not directly connected to the mainstem of the Yangtze River, i.e. Lake Gehu, Lake Dianshan and Lake Yangcheng, to analyze the characteristics of optical composition of CDOM under the wet, wet-to-dry transition, and dry hydrological scenarios. Using parallel factor analysis, we obtained two humic-like (C1 and C4) and two protein-like (C2 and C3) components. High fluorescence intensity (F_max) of protein-like components in the three lakes were observed in all these lake with surrounding high urban land use, and the R² of linear fittings of correlation between protein-like components and chlorophyll-a concentration were low, indicating that the protein-like components were affected by both algal degradation and anthropogenic effluents. The mean of F_max of protein-like components and total nitrogen concentration in the three lakes were significantly higher in dry season than in wet season, indicating that increased rainfall can dilute the concentration of dissolved organic substances in these lakes. Significant positive correlations were recorded between humic-like materials and dissolved organic carbon, total nitrogen, total phosphorus, chlorophyll-a. Meanwhile, with increasing rainfall, the contribution percentages of protein-like components decreased from 86.84% to 62.49% in Lake Gehu, and from 96.53% to 90.56% in Lake Dianshan, and from 98.40% to 96.26% in Lake Yangcheng, indicating that rainfall events could also enhance the erosion soil leachates and discharge more soil organic-rich substances into the lakes. We concluded that rainfall events and human activities altogether acted on the CDOM dynamics in the three lakes, and our results enriches the research data on carbon cycling in these lakes and improves our knowledge on making advanced schemes for the protection of water supply security in the Taihu Basin.