It was the first time to study the types and immunological functions of blood cells in bloody clam(Scapharca broughtonii)by the means of microscopic observation and immunostimulation with pathogenic Vibrio anguillarum,and three types of hemocytes were recognized:red blood cells,white blood cells and thrombus cells.Red blood cells had four developmental states:freshmen,mature,aging and death.White blood cells were divided into acidophils,neutuophils,basophils,lymphocytes,and megalokaryocytic.Acidophils,neutuophils,basophils and thrombus cells were all involved in the blood coagulation.Both red blood cells and white blood cells had phagocytic function,red cells showed the passive phagocytic function and immune adherence function,while white cells showed the active phagocytic function.Acidophils and neutuophils cells were principal in phagocytizing pathogens,and basophils cells could be found phagocytizing large size foreign materials,an increase in the number of white cell and inflammation took place after the bloody clam was infected by pathogen.It was also the first time to show the thrombus cells and its coagulation function in bloody clam(Scapharca broughtonii).The results showed that the blood cells had systemic immunologic defense mechanisms against the mass pathogens invasion into the body of bloody clam(Scapharca broughtonii).