Acid volatile sulfides (AVS) in surficial sediments from Wuli lake, Lake Taihu, 2002 are available for binding with divalent cationic metals through the formation of insoluble metal-sulfide complexes, thereby controlling the metal bioavailability and subsequent toxicity to benthic biocommunities.AVS concentrations and simultaneous extracted metals (SEM) values are determined have become the major research topic associated with sediments.The ratio of SEM to AVS is promising to predict metal toxicity.From investigated AVS and SEM during summer and autumn at five locations of Lake Taihu, it was found that SEM-AVS values and AVS concentrations did vary significantly between locations during both seasons.AVS concentrations were greater during summer than spring;SEM concentrations did not significantly vary between seasons at the same location, which resulting in significantly lower SEM-AVS values in summer.SEM-AVS values were greater than one at each location during both seasons illustrated there might exist heavy metals toxicity in Lake Taihu sediments.