Based on the survey of the species abundance, biomass per unit water volume and species diversity indices of plankton and benthos along the west shore of Taihu Lake, we analyzed the characteristics of the Hydrobios distribution in this area. Five phytoplankton families were found in the survey, and the species of Cyanophyta and Chlorophyta accounted for 46.81% and 36.17% of total species abundance, the biomasses of these species were 60.97% and 34.49% of total algae biomass, respectively. In contrast, the biomass of species of Bocillariophyta accounted only for 3.07% of total algae biomass. The Shannon-Wiener diversity index and Even index generally fluctuated from 1.3 to 1.6 and from 0.14 to 0.22, respectively. Of the 71 species of zooplankton found in current survey, pollution-tolerant copepodas and cladocerans accounted for 36.62% of total species, and their biomass per unit water volume could reach 7.07×10⁴ind/L and 7.76×10⁴ind/L, respectively. The zoobenthos along the shore showed a simplified community structure, the abundance of environment-sensitive species decreased greatly and some species became extinct. Species diversity index of zoobenthos community along the shore was very low, with diversity index and even index only about 1.59 and 0.581, respectively. Meanwhile, some pollution-tolerant and cosmopolitic species propagated rapidly, and their biomass per unit water volume accounted for 84.76% of total biomass of zoobenthos. Through a evaluation based on a combined method (dominant-species assessment and diversity index assessment), we concluded that the water quality along the west shore of Taihu lake showed a sign of severe eutrophication. This conclusion could also be confirmed by the results of monitoring of water quality at 24 sites of the estuary, which showed that the concentration of Total Nitrogen (TN) and Total Phosphorus (TP) were 3.50 mg/L and 0.28 mg/L, higher than the V standards (TN≤2.0 mg/L, TP≤0.2 mg/L) of National Lake Water Quality Standard.