The correlation between hemolysis time and concentration of saponin(2.5,5,12.5,25,50 and 125 mg/L)was analyzed via microscope observation.In vitro hemolysis rate of turbot blood cells in different concentrations of saponin(2.5,5,12.5,25 and 50 mg/L)at 20 and 4 ℃,for different time duration were tested respectively.To investigate the toxicity of saponin extracted from Quillaja saponaria to turbot(Scophthalmus maximus),median lethal concentration(LC50)was calculated by immersing the turbot in sea water with different concentrations of saponin.In addition,the lactic dehydrogenase(LDH)activities in serum of turbot after bathing in saponin seawater solution(0,5,25 and 45 mg/L)were analyzed.The results indicated that the correlation between hemolysis time of erythrocytes and saponin concentration showed a logarithmic negative correlation(R²=0.98),and that saponin could also induce hemolysis to leukocytes of turbot.Saponin in concentration of 50 mg/L could result in 100% hemolysis at 20 ℃ for 5 min,in contrast,only 42.2% hemolysis was observed at 4 ℃.The 24 h LC₅₀ of saponin for S.maximus was 64.85 mg/L.In this report,from cell level,the evaluation of the toxicity of saponin to blood cells for hemolysis was made,which will theoretically support its safe application in aquaculture.