The types and distribution of mucous cells stained with AB-PAS (AB,pH2.6) in the gill and digestive tract of Hippocampus japonicus and Hippocampus trimaculatus were studied. The results shows that the gill and digestive tract of Hippocampus japonicus and Hippocampus trimaculatus has mucous cells. There are types Ⅱ, Ⅲ and Ⅳ mucous cells in the gill of Hippocampus japonicus and Hippocampus trimaculatus. The mucous cells’s types and amount is different among the parts of digestive tract. There are most TypeⅠ cells in the esophagus of Hippocampus japonicus while there are most type Ⅳ cells in the esophagus of Hippocampus trimaculatus. Hippocampus japonicus?s small intestine only have type Ⅰ, however, all three types (typeⅠ, type Ⅲ and type Ⅳ ) are founded in the small intestine of Hippocampus trimaculatus and among the three types type Ⅰcells exists most. Furthermore, three types (typeⅠ, type Ⅲ and type Ⅳ)cells are also founed in the large intestine of Hippocampus japonica ,but there are more type III cells in the large intestine of both Hippocampus japonica and only type I cells in the large intesting of Hippocampus trimaculatus. Four types (type I, type II, type Ⅲ and type Ⅳ) cells are discovered in the rectum of both Hippocampus japonicus and Hippocampus trimaculatus. The rectum of Hippocampus japonicus have most type Ⅲ cells while the rectum of Hippocampus trimaculatus have most type Ⅳ cells.