Focusing on the sediment in Suyahu Reservoir (a typical plain reservoir in Henan Province, China), concentrations of eutrophication-causing substances (TOC, TN and TP) and heavy metal contamination (Zn, Pb, Cd, Cu, Cr, Ni, As and Hg) were measured. Spatial distribution of these contaminants and the resulting potential ecological risk were investigated in detail. The results indicated that the eutrophication-causing substances were concentrated in the reservoir sediment, with high concentrations in the south and low concentrations in the north due to hydrodynamics. The reservoir sediments were polluted and had an eutrophication problem due to the high average organic index. Heavy metals were deposited at the bottom near the centre of the reservoir. The comprehensive potential ecological risk index was Moderate, whereas Cd and Hg contributed 78.8% to the total risk-index values, and were the main factors of heavy mental pollution. Therefore, it was necessary to prevent and treat polluted sediments to prevent secondary pollution.@en