Abstract: Objective To study hepatotoxicity and superoxide dismutase(SOD)activity produced by oscillatoria-extract in vivo.Methods Hepatotoxicity and superoxide dismutase(SOD)activity of oscillatoria-extract were detected by ip in mice.Results The liver weights were increased consistently during three weeks treatment.It was showed in histology study thathepatocytes swelling,necrosis and congestion with blood in venae interlobares hepatis.The SOD activity of liver and blood decreased after one week treatment but increased the following two weeks treatment.Conclusion Oscillatoria-extract had obvious hepatotoxicity and a certain lipid peroxiodation effect in vivo.The relationship between oscillatoriales pollution in water and hepatocarcinoma prevalence in Tongan area needed further research.