The research was conducted on the states and properties of the substances near the sediment-water interface (SWI) in Lake Taihu and its potential impact on water quality by field sampling and laboratory testing at 39 sampling sites in eight regions of Lake Taihu. This paper analyzed the states and vertical composition of sediments, especially the substances near the SWI in different regions, and the relationship between the sediments, phosphorus release and outbreak potential of black bloom. The results indicated that three types of substances exist on the SWI of Lake Taihu:silty hard clay, soft silt and suspended layer. Silty hard clay is a ubiquitous basement sediment in the whole lake, which is directly exposed in the central area and the other parts of the lake. Soft silt is a sediment formed in the lacustrine facies' history, covering 68% of the bottom and directly contacting with surrounding water. Suspended layer appears in areas having higher particulate matter input in recent years. Among four types of vertical structures of the sediment, type Ⅰ and type Ⅱ have relatively limited impact on the water, while type Ⅲ and type Ⅳ are easy to release nutrients into water. In this research, high content of organic matter and total phosphorus were found in the suspended layer. The location of the suspended layer was consistent with the black bloom area, which indicates that the suspended layer has negative influence on the water quality in Lake Taihu.