The histological structure of the digestive tract of Siganus canaliculatus was studied by using light and electronic microscopy. The esophagus mucosa was composed of stratified squamous epithelium with many mucous cells and there were lots of glands in the submucosa. The stomach mucosa formed with a singlelayered columnar epithelium. The gastric cardiacus and caecum contained many glands while the gastric pyloricus contained less. The gastric columnar cells included more mitochondrion, rough endoplasmic reticulum and Golgi apparatus, some of cells had many pinosomes. The intestine epithelium was also singlelayered columnar epithelium, including a great number of goblet cells. Dense microvilli were observed on the free surface of the epithelium, junctional complex was present on its lateral edge and, abundant cell organs were present in its cells. There were a lot of multivesicular bodieson at the top of the epithelium cell of the intestine. With changes from foregut to hindgut, the height of folds decreased and the number of folds was reduced gradually, in addition, the muscular coat became much thicker. Large numbers of lymphocytes were distributed in the hindgut, which closely arranged in ring. The histological character of the pyloric caeca was similar to the intestine’s, but the epithelium cell of the pyloric caeca had denser multivesicular than the intestine’s. The results showed that there was close correlation between the characteristics of histology structure in digestive tract and digestion and absorption of S. canaliculatus.