Abstract: As an important storage lake and water source of the east route of South-to-North Water Transfer Project, Luoma Lake's water environment safety has a far-reaching impact on northern Jiangsu and even the east route of South-to-North Water Transfer Project. By analyzing the Pb content and Pb isotopic composition of the surface sediments of Luoma Lake and rivers into the lake, and the soil of potential pollution sources in the surrounding areas, the spatial distribution of lead was evaluated. The ecological risk assessment of heavy metal Pb was carried out by using the enrichment coefficient method, and the binary linear mixed model was applied to analyze the polluting sources and calculate the relative contribution rate of each source. The results showed that the content of Pb in surface sediments of Luoma Lake ranged from 8.09 to 27.97 mg/kg, with an average of 20.94 mg/kg, and Pb in surface sediments of Luoma Lake showed a clean-slight pollution level. Spatial analysis showed that Pb pollution of surface sediments in Luoma Lake was mainly concentrated in the eastern and northern lakes. The values of ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/(²⁰⁶Pb+²⁰⁷Pb) (the ratios of abundance) in the surface sediments of Luoma Lake were 1.170-1.249 and 1.125-1.131, respectively, and the Pb pollution mainly came from the Laoyi River and the direct discharge of agricultural pollution from fishery farming. The relative contribution rate of agricultural sources was 46.71%. In order to prevent and control the pollution risk of Pb in Luoma Lake water environment, it was necessary to strengthen the standardized management of fishery culture and the pollution control of rivers entering the lake.