Abstract: Five healthy nile tilapia(average weight 500g) were bought.After executing,the esophagus,stomachus(stomachus fundus,stomachus pylorus and stomachus cardiacus),small intestine(foregut,midgut and hindgut) were respectively fixed in the Carnoy solution(60% dehydrate alcohol,30% chloroform and 10% glacial acetic acid),con-tinuously embedded and sliced with 6μm.Toluidine blue staining(MTB),Alcian blue Safranin O staining(AB/SO),methyl green-Pyronine staining(MG-P),Azure Ⅱ-Eosin-Wright mixture staining and Thionine staining were used to investigate the histochemical property of the mast cells in the digestive tract of tilapia. The mast cells were showed in the esophagus,stomachus and small intestinal wall of nile tilapia.The mast cells in the slides of esophagus and stomachus mostly distributed between lamina propria and stomachus gland.The mast cells in intestinal tract mainly distributed in lamina propria and under intestine epithelium,while less in connective tissue of submucosa.They were circular,ellipse and spindle,and intended to be around blood vessels.The results of five histo-chemical stainings were as follows: The MTB,AB/SO and MG-P stainings could show the mast cells better,especially the AB/SO was the best among them.The mast cells were distinctly outlined,the cytoplasmic particle of which was clear.The similarity of the research on teleostean mast cells from home and abroad was that the mast cells of nile tilapia was similar to mucosal mast cell of mammal.The effect of MG-P staining was good too,in which the cytoplasmic par-ticle of mast cells showed red,which meant the cytoplasmic contained mainly heparin not histamine.It confirmed fur-ther that the histochemical property of the mast cells of nile tilapia was similar to mucosal mast cell of mammal.The effect of Azure Ⅱ-Eosin-Wright mixture staining was better,but the mast cells dyed was few.Whereas,the mast cells in the sections of digestive tract of nile tilapia could not been showed by 80% Alcohol-Thionine staining.The reason might be different stationary liquid or the difference in histochemical property of mast cells of nile tilapia,carp and white fish.The observation showed that the mast cells in the digestive tract of nile tilapia mostly distributed in the points which easily revealed from environment antigen such as shallow mucosa or blood vessels,the connective tissue around gland and so on.The mast cells had similar distribution characteristics in different organs of other animals.From the above,the distribution characteristics of creatural mast cells were closely bound up with the function of cell,which maybe provide handy positional foundation for the exertion of autoimmune function in a sense.The experiment also found that the location of mast cells in connective tissue of mucosa in digestive tract of nile tilapia were similar with most of the vertebrate,of which the location was intended to be around blood vessels.It meant that teleostean mast cells were closely related to blood vessels as mammals were. It was reported that the growth of vascular endothelial cells and constitute of blood circulation were affected by histamine and heparin released from mast cells.The vascular endothelial leukocyte adhesion molecule 1,which could watch blood stream by attracting lymphocyte adhere to the inner wall of blood vessels,could be induced by Tumor Ne-crosis Factor-α(TNF-α) released from mast cells in human skin.It was obviously that the mast cells around blood ves-sels played an important role in reaction of blood vessels.