Blooming of Chattonella marina has caused massive fish kills and considerable economic loss in recent years along the southern coast of China.However detailed toxic mechanisms involved in these fish kills still remain uncertain.Hemolytic toxins produced by C.marina has been suggested to be the major causative factors for the observed fish kills.The extraction of hemolytic toxins from Chattonella marina Hong Kong strain(CMHK) was investigated in laboratorial conditions.The haemolytic process of the extraction from CMHK to red cells was observed with microscope.Hemolytic toxins were separated with TLC.The results showed that optimal condition for breaking the cell walls of algae by ultrasonic was 400 w of power for 15 minutes at 4℃,and the hemolytic toxins synthesized by CMHK could consist of at least 4 components,which included one lipid and three glucolipid fractions.The hemolysin toxins could break the red blood cells of rabbits(RBCs) through its hydrophobe group linking to the surface of RBCs.These findings will be of great significance for the future studies on the toxic mechanisms.