Abstract: The aim of this study is to evaluate the distribution and potential ecological risks of heavy metals in the water environment of Puding Reservoir in the upper reaches of the Wujiang River. The spatiotemporal distribution and content of six heavy metals (Hg, As, Cu, Ni, Cd, Pb) in the sediments were investigated in 2018. The comprehensive pollution index, geo-accumulation index and potential ecological risk index were used to determine the general pollution characteristics of the trace metals in surface water and sediments. The results indicated: (1) The contents of Hg, As, Cu, Ni, Cd, and Pb in the surface water of Puding Reservoir were (0.004±0.003)(0.050±0.044)(4.225±3.117)(18.343±17.093)(0.845±0.739) and (6.155±5.747)μg/L, respectively. Among them, the concentrations of Hg, As, Ni, Cd, Pb had similar patterns in seasonal variation, which displayed as winter > autumn > spring > summer. The content of DO was significantly correlated with Hg, As and Cu, which indicated that the concentrations of some heavy metals could be affected by DO. (2) The contents of Hg, As, Cu, Ni, Cd, and Pb in the surface sediments of Puding Reservoir were (0.06±0.02)(14.75±4.88)(166.60±74.74)(87.43±51.18)(1.89±0.26) and (206.34±110.33)mg/kg, respectively. Among them, the average contents of Pb, Cd, and Cu were respectively 6.0, 5.8, 5.0 times of the soil background value in Guizhou Province. There were seasonal differences in the distribution of heavy metal content along the course. The contents of Cd, Pb, Hg, Cu, and Ni were the highest in autumn and winter. The contents of Cd, Pb, Hg and other elements gradually increased from upstream to downstream. When it reached the maximum value, it showed obvious spatial distribution characteristics, indicating that heavy metal pollution along the route gradually increased. (3) The integrated pollution index method showed that the water quality of Puding Reservoir was good, and it was not polluted by heavy metals. The Geo-accumulation index method showed that the surface sediments of Puding Reservoir were polluted mainly by Cu, Ni, Pb, and Cd. The potential ecological risk index method indicated that Cd and Pb had higher risk values and were the main source of ecological risk of heavy metals in Puding Reservoir. Therefore, special attention should be paid to the prevention and control of Cd and Pb in the treatment of heavy metals in Puding Reservoir. According to the results of heavy metal assessment, the heavy metal pollution in the water environment of Puding Reservoir was mainly caused by external pollution. Mining and smelting activities may be one of the main reasons for the high content of heavy metals. Therefore, it is necessary to strengthen the comprehensive treatment of heavy metals in the water environment of Puding Reservoir, especially Cd and Pb pollution.