Abstract: 【Objective】 Study the effects of a dam on heavy metal distribution in sediments.【Methods】We used a two-step approach to understand the influence of a dam on sediment deposition and heavy metal distribution. The first step was to evaluate the effects of dam construction on sedimentary characteristics based on the changes in hydrological conditions by using One-way analysis of variance(ANOVA). The second step applied redundancy analysis to examine the relationship between heavy metals(As, Cr, Pb, Cd, Cu, Hg and Zn)contents and the physical and chemical properties of sediments, including grain size distribution and organic carbon content. The Suo River was selected as the study area, which was divided into three parts(up, middle and down)according to the direction of the water flow and the position of the dam. 【Result】 The hydrological conditions in each part showed marked differences: the up part regularly showed a state of river blanking, the middle part had low water flow, and the down part always contained water. The reservoir-dam construction affected these characteristics and distribution of sediments. Analyses results of grain size distribution showed silt and clay depositions were higher in the middle part than those recorded in the up and down parts. Silt represented the largest proportion of sediments in all samples, whereas clay comprised the lowest percentage. Reservoir-dam construction resulted in an abundance of tiny grains of sediment in the middle part, and the organic matter also deposited in the middle part, depending on the flow regime and flow rate of the river. One-way ANOVA analysis showed that the distributions of heavy metals contents were high in the middle part, except Cr and Cu. Redundancy analysis showed that the grain size played a significant role in controlling heavy metal content in sediments, as the content tended to increase with declining grain size. 【Conclusion】Overall, reservoir-dam construction increased the risk of heavy metal pollution by changing the hydrological conditions.