Abstract: Types and distribution of mucous cells in the digestive tracts (i.e., tongue,esophagus,stomach,and intestines) of Lateolabrax japonicus were observed and analyzed by using AB-PAS (alcian blue and periodic acid schiffs reaction) and Alcine Blue staining at different pH (pH1.0,2.5,and 3.1).According to AB-PAS,4 types of the mucous cells in the digestive tracts of L.japonicus were observed: TypeⅠ,Ⅱ,Ⅲ and Ⅳ.TypeⅠwas pure red,AB negative and PAS positive containing neutral mucoitin.TypeⅡ was pure blue,AB positive and PAS negative containing acidic mucoitin.Type Ⅲ was purple reddish,both AB and PAS positive,PAS positive more than AB containing mainly neutral mucoitin and a few acidic mucoitin.TypeⅣ was blue purple,both AB and PAS positive,AB positive more than PAS containing mainly acidic mucoitin and a few neutral mucoitin.The Alcine Blue staining at pH2.5 and pH3.1 showed blue from the acidic mucous, and at pH1.0,either weak or strong blue from the vitriolic acidity mucous.The statistical results showed that in different parts there were different types and densities of mucous cells.Only a small quantity of mucous cells existed in tongue,mostly typeⅡ.On the other hand,large quantities of mucous cells were found in esophagus,stomach,and intestines.Most of them in esophagus and intestines were of Type Ⅲ and Type Ⅳ,and all of the mucous cells in the stomach belonged to TypeⅠ.The types and distribution of mucous cells closely related to the functions of the organs where they were found.