The types and distribution patterns of skin mucous cells in three species of benthic freshwater fishes were analyzed with conventional paraffin sections and AB-PAS staining method. We divided the mucus cells into four groups, type Ⅰ cells were red, type Ⅱ cells were blue, type Ⅲ cells were amaranth, and the type Ⅳ cells were bluish violet (Fig. 1). The numbers of mucous cells in head, back, belly and tail of these three kinds of fishes were counted in 10 visual fields (the area of visual fields was 43.5 μm × 32.6 μm), and the average number of mucous cells was calculated. Using One-way Anova, we compared the number of four types of mucous cells in Perccottus glenii, Pelteobagrus fulvidraco, and Misgurnus anguillicaudatus. Results showed that representative mucous cell type was different in different kinds of fishes, which might be related to the pH of the water in which they live. The acidity and alkalinity of fish mucus was often balanced with the environment. In mucous cells of Perccottus glenii, the majority was type Ⅲ which contains plenty of neutral mucopolysaccharides and some acid mucopolysaccharides. Its number was 61.5% more than that of type Ⅰ cells, 85.8% more than that of type Ⅱ cells, 85.7% more than that of type Ⅳ cells. On the body surface of Pelteobagrus fulvidraco, the number of type Ⅰ mucous cells accounted for the majority, and they mainly contained neutral mucopolysaccharide. Their number was 9.9% more than that of type Ⅱ cells, 15.1% more than that of type Ⅲ cells, and 53.5% more than that of type Ⅳ cells. On the body surface of M. anguillicaudatus, type Ⅱ cells accounted for the most, and they contained a lot of acid mucopolysaccharides. Their number was 88.3% more than that of type Ⅰ cells, 33.1% more than that of type Ⅲ cells, and 83.5% more than that of type Ⅳ cells (Table 1). Acid mucopolysaccharides were widely distributed on the mucous surface of the skin in all three species of fishes, and they might have important immune function to fishes, helping to remove germs and harmful substances from the environment, and playing a vital role in normal physiological activities. The number of mucous cells varied from part to part, and forepart trended to have more mucous cells than the back. For Perccottus glenii, mucous cells were mainly distributed on head, the number of mucous cells in the back was 15.4% more than that in the back, 38.0% more than that in the abdomen, and 56.7% more than that in the tail. The mucous cells of Pelteobagrus fulvidraco were mainly centralized on the back, the number of mucinous cells in the head was 42.5% more than that in the head, 46.6% more than that in the abdomen, and 51.4% more than that in the tail. M. anguillicaudatus also possessed rich mucous cells on the back, the number of mucinous cells in the back was 49.9% higher than in the head, 50.6% higher than in the abdomen, and 43.8% higher than in the tail (Table 1). The total numbers of mucous cells in the three species were different. There were more mucous cells in non-phosphorous fish than in squamous fish. The whole body′s mucus cells of M. anguillicaudatus or Pelteobagrus fulvidraco were more than that of Perccottus glenii, and moreover, the total number of mucous cells on the body surface of M. anguillicaudatus accounted for the most, 38.9% more than that in the Perccottus glenii, and 39.1% more than that in the Pelteobagrus fulvidraco. The types of mucous cells on the body surface of different kinds of fishes were different, which may relate to the living environment or their own characteristics. The Acid-alkaline of fish mucous cells is the same as that of environment. In addition, the distribution of mucous cells is related to the species of fish and the location of distribution.