Abstract: Ammonia nitrogen, as one of the main pollutants, have toxicity to organisms under high concentration in aquatic ecosystem. It has been widely reported about the negative impacts of ammonia on the behavior, growth and reproduction of organisms. However, the previous studies were mainly focused on fish, rarely studies were conducted with zoobenthos and limited to small scale experiments. To explore the toxicity of ammonia on zoobenthos, we conducted a one-year semi-natural experiment in 6 ponds (ca. 600 m² in surface area; ca. 1.5 m in depth) located in Hubei Province and analyzed the difference of zoobenthos (mollusc) community under 6 ammonia concentrations N25>N20>N15>N10>N5>N0 (control; 0.2—33.7 mg/L. The result showed that: (1) the mollusc identified during the experiment was mainly Bellamya aeruginosa; (2) N0, N5, N10 and N15 treatments had similar B. aeruginosa density 28(0—85) ind./m², which were significantly higher than that in N20 and N25 treatments 5(0—29) ind./m² (P<0.05); (3) N0, N5, N10, N15 and N20 treatments had similar B. aeruginosa biomass 40.0(0—85.5) g/m², which were significantly lower than that in N25 treatment 0.8(0—4.0) g/m² (P<0.05); (4) shell length, shell width and body mass of B. aeruginosa were the lowest in N0 treatment, while which were the highest in N20 or N25 treatment; (5) B. aeruginosa density and biomass were negatively correlated with ammonia concentration significantly (P<0.05), and decreased with the increasing non-ionized ammonia concentration; (6) shell length, shell width and body mass of B. aeruginosa were positively correlated with non-ionized ammonia concentration significantly (P<0.05), and increased with the increasing nonionized ammonia concentration. The results suggested that ammonia concentration higher than 21.7 mg/L and non-ionized ammonia concentration higher than 0.18 mg/L (annual mean value in N15 treatment) had significantly negative impact on mollusc, especially for its reproduction, while no negative impact was found on the growth of individuals. More phytoplankton induced by ammonia loading may provide more food for mollusc which was advantageous for the accumulation of carbohydrate and help to detoxify the body. The shelter from sediments might have released B. aeruginosa from ammonia exposure as the non-ionized ammonia concentration was lower at the bottom layer near the water-sediment interface compared with that at the surface layer. This study could help to develop the understanding of ammonia toxicity to mollusc and may improve scientific basis for nitrogen management in aquatic ecosystems to a certain extent.