Abstract: By using immunocytochemical method of Strept Avidin-Biotin-Complex(SABC), 4 kinds of antisera raised against rabbit hormones were used to identify and locate the endocrine cells in the gastrointestinal tract of mandarin fish(Siniperca chuatsi). Results showed that glucagon(Glu)-and gastrin(Gas)-immunoreactive endocrine cells were not found in the gastrointestinal tract of mandarin fish; somatostatin(Som)-, and serotonin(5-HT)-immunoreactive endocrine cells were found in the cardia, pylorus and gut of mandarin fish in varying degrees. There were distributions of Som-immunoreactive endocrine cells between epithelium cardia and cardiac gland, and between epithelium pylorus and pyloric gland; their distribution in the cardiac gland and pyloric gland was denser than in the epithelium cardia and pylorus. There were more 5-HT-immunoreactive endocrine cells in the fundus vertriculi and intestinal epithelial tissue. Also there were more 5-HT-immunoreactive endocrine cells in the neurones of nerve plexus in muscle layer. These peptidergic neurones contained serotonin have the typical characteristic of APUD(Amine Precursor Uptake and Decarboxylation)cells. It is a prompt that as in the mamalian also there are many peptidergic neurones in the gastrointestinal tract of fish. It provided morphological basis for the research of neuro-endocrine system.