[Objective] The research aimed to study the toxicity effect of microsystin on Hydra（aquatic animal model）.[Method] Hydra magnipapillata was as the experimental material.Under the different concentrations of MC-LR solution,its acute toxicity effect on Hydra magnipapillata was observed.[Result] The half lethal concentration（LC50） of MC-LR on Hydra magnipapillata at 24 h was 12.158,4.029 mg/L at 48 h and 1.799 mg/L at 72 h.[Conclusion] Hydra magnipapillata would die when treated by the low concentration of MC-LR solution.It illustrated that MC-LR produced by algal blooms caused the damage on some aquatic animals,and even some low-level aquatic animals died,such as Hydra magnipapillata and so on.The research provided some reference basis for the detection and assessment of water body pollution.
