Abstract: In recent years, with the rapid economic development of the Yangtze River Basin, the local government has attached great importance to the deterioration of the water quality of Nanyi Lake, the lake of the South Bank of the lower reaches of the Yangtze River. In this study, 39 samples were collected from surface sediments of the whole lake area and 6 surface water samples from the main inlet and outlet tributaries, and the contents and distribution patterns of heavy metals As, Cr, Cu, Mn, Ni, Pb, Zn and the contents of TOC and TN in the sediments of Nanyi Lake were analyzed.The pollution degree and ecological risk of heavy metals in sediments were evaluated, and the pollution sources of Nanyi Lake were analyzed by principal component analysis and correlation analysis.The results showed that the average concentration of Pb in interstitial water exceeded the Criteria Continuous Concentration (CCC) of the National Recommended Water Quality Criteria.The average contents of As, Cr, Cu, Mn, Ni, Pb and Zn in sediments were higher than the river background value in the Jianghuai River Basin of Anhui Province, and the multiples exceeding the background value were Pb (3.36)>Mn (2.74)>Zn (2.51)>As (1.80)>Cu (1.40)>Ni (1.34)>Cr (1.13). Fractions of heavy metals analysis showed that As, Cr, Ni and Pb existed mainly in residual fractions (F4), while Zn was dominated by the non-residual fraction ( F1 + F2 + F3) with a mass fraction of 54%, and the reducible fraction (F2) of Mn was 37.4% in East Lake, the sulfide and organic matter bound state (F3) of Cu in the West Lake accounted for 26.7%. The potential ecological risk assessment method of heavy metals showed that Pb was a medium-risk in 13 sampling site. The average value and order of heavy metal partition coefficient (lgKd) in sediments were Cr (4.80)>Zn(4.50)>Cu(4.43)>Pb(4.37)>Ni(4.31)>As(4.27)>Mn(2.73). The principal component analysis and correlation analysis and spatial distribution showed that the water pollution of Nanyi Lake mainly came from the industrial wastewater collected by the rivers entering the lake, aquaculture and aquatic biodegradation in the lake, as well as the non-point source input from the surrounding agriculture and residents' lives. Based on the high ecological risk of Pb in the whole lake area, we should continue to pay attention to the impact of heavy metal Pb on the water environment and ecosystem of Nanyi Lake.