Corbicula fluminea is the dominate species among the large benthic organisms in Lake Taihu.A controlled experiment was conducted to assess the effects of C.fluminea on water quality improvement with four treatments of different densities of C.fluminea of Lake Taihu.C.fluminea was put in four groups:the none, low, medium and high densities were designed as 0 g/m² (control group), 130 g/m², 260 g/m², 520 g/m², respectively.The results showed that, in contrast with the control group, the concentrations of suspended particulate materials of water in low, medium and high density groups significantly reduced by 20.85%, 34.90% and 53.79%, respectively.Moreover, chlorophyll-a concentrations significantly reduced in C.fluminea treatments with the decrement of 23.29%, 48.32% and 71.17%, respectively from the low to high density groups.Meanwhile, total nitrogen and total phosphorus concentrations of water reduced in C.fluminea groups, while no significant difference showed between medium density and high density treatments.It revealed that C.fluminea could purify eutrophic water by filter-feeding phytoplankton and organic suspended materials, lowering the water turbidity, and improving light conditions, which was conducive to the growth of periphyton on the lake bottom and the restoration of aquatic plants.It is suggested that C.fluminea has an important ecological significance to the restoration of eutrophic waters.However, in terms of Lake Taihu, the effect of C.fluminea on the water quality improvement may be hampered by resuspension process which releases nutrients from the water-sediment interface.