Abstract: The presence investigation and morphology observation of 5-HT endocrine cells have been carried out with the anti-5-HT serum by the method of the ABC immunhistochemical technique in the digestive tract of Elaphe dione.The results indicate that the distributive density of 5-HT cells is maximum in the duodenum and minimum in the cardiac part of stomach,and the density curve of 5-HT cells in gastrointestinal tract appears reverse "V".The shape of 5-HT endocrine cells is diverse.The cells in superior segment (esophagus,and stomach) are round or ellipse,and disperse the bottom of epithelial or between gland epithelial cells mainly;those in middle segment (duodenum,jejunum,and ileum) are tapering,shuttle and round,and disperse the bottom of epithelial or between epithelial cells mainly;those in inferior segment (rectum) are round and disperse the bottom of epithelial cells.The tapering cells always have one long processus extending to either the gut lumen or lamina propria,and perform exocrine or endocrine function;the shuttle cells have two long processuses,one extending to gut lumen,the other extending to lamin propria,and perform both exocrine and endocrine functions.