Abstract：Large reservoirs supply drinking water to metropolitans and large cities， and serve as flood regulator and provide water for farmland irrigation， tourism， and entertainment. Drinking water reservoirs are widely distributed in the hilly areas of Anhui and Zhejiang Provinces， and these waters encounter certain water quality risks in the summer with the proliferation of algae cells and release of algal-derived chromophoric dissolved organic matter （CDOM）. We used total nitrogen （TN）， total phosphorus （TP）， chlorophylla （Chl a）， Secchi disk depth （SDD）， and calculated trophic level index （TLI） based on these four indices， together with CDOM absorption and fluorescence spectroscopy to unravel the sources and optical composition of CDOM in a total of 12 drinking water reservoirs in Zhejiang and Anhui Provinces. Our results showed that the drinking water reservoirs were mostly mesotrophic with TLI ranged from 25.0 to 48.8 and a254 ranged from 7.0 to 10.2 m-1. we found Chl a， TLI， a254， and terrestrial humic-like C2 increased with increasing concentration of TP （p<0.01）， indicating that TP was a major influencing factor controlling algal growth in drinking water reservoirs and TP was closely associated with TLI. The average concentration of Chl a was （8.4±5.7） μg·L-1， and we found no significant correlation between Chl a and tyrosine-like C1 or tryptophan-like C3（p>0.05）， indicating that rapid algal degradation contributed insignificantly to the CDOM pool in those reservoirs. Terrestrial humic-like C2 showed a significant positive correlation with a254 （r=0.81， p<0.01） and Chl a （r=0.37， p<0.05）， and TLI increased with increasing humification index （HIX） and with decreasing spectral slope S275~295in the open water region， indicating that terrestrial input of organic substances contributed importantly to nutrient levels in the open waters of the studied reservoirs. The mean of S275~295 was （23.2±2.8） μm-1， corresponding to a mean HIX of 1.56±0.62， indicating a relatively low aromaticity of CDOM in the drinking water reservoirs， likely due to a high SDD and enhanced photodegradation of CDOM， and thereby a low apparent terrestrial signal of CDOM in those waters. The regression coefficient of a254， terrestrial humic-like C2 and TLI were low， suggesting that we should be more cautious when terrestrial humic-like components were applied to the estimation of nutrient levels in open water areas of large reservoirs.