Acid-volatile sulfides (AVS), which can form insoluble sulfides complexes with minimal biological availability with a number of cationic metals, is a key partitioning phase controlling metal bioavailability in the sediments. Toxic effects were found to be absent for SEM/AVS ratios smaller than one, but appeared to be present at SEM/AVS ratios exceeding one. This study investigated the vertical distribution of SEM (Cu, Zn, Pb, Cd, Ni, Co, Ag, Cr) and SEM/AVS ratio in the sediments cores of three different polluted stations in Lake Donghu, Wuhan. It was found that the metal concentrations were in the order of Zn > Cr > Cu > Ni≈Pb>>Ag≈Cd. Among heavy metals, Zn, Cr and Cu were the dominating species, accounting for nearly 90% of SEM. At Station I and Ⅱ, AVS was the key factor to control the bioavailability of metals, and SEM/AVS ratios were less than one. Significant linear relationship between AVS and metals at Station I and Ⅱ confirmed that AVS had a great effect on the vertical distribution of metals. However, at Station Ⅲ, SEM/AVS ratios were larger than one, and no significant linear relationship between AVS and metals was found. The sediments in Station Ⅲ have potential metal toxicity. Significant linear relationships were observed between trace metals (Cr, Ni, Ag, Cd) and AVS at Station I and Ⅱ, indicating that these metals were associated to the AVS phase in the sediments more than other metals. Especially there was a close relationship between SEM-Ag and AVS in the sediments at both stations (r=0.6973, Station I;r=0.7786, Station Ⅱ). Our results also show that there was a higher SEM-Cr/AVS ratio in the sediment with high AVS (Station I, r=0.7129) than in the sediment with low AVS (Station Ⅱ, r=0.4114) while SEM-Cr level did not differ significantly in both stations. It seems likely that Cr is strongly influenced by complex redox reaction pathways rather than simple substitution reactions, and tends to be absorbed on, or coprecipitate with iron sulfide phases in an anoxic environment more than a slight anoxic environment.