| The number, histological characteristics, types and distribution of mucus cells in the pyloric caecum of Siniperca chuatsi at different developmental age were observed and described by histology sectioning, H.E and AB. PAS stainings. The results showed that at 15 days after hatching, there was a cluster of pyloric caecum began to develop on the left ventral side between the stomach and intestinal. At 20 days after hatching, there was a cluster of pyloric caecum developed on the right ventral side below the intestinal tract, and at 25 days after hatching, there was a cluster of pyloric caecum developed on the right ventral side between the stomach and intestinal side, and the left ventral side below the intestinal, respectively. At the age of 20, 30, 40, 50 and 60 days, the number of pyloric caecum were 25±2, 75±2, 123±4, 155±7 and 190±5, respectively. The number and the length of the fold and the thickness of the muscular layer of pyloric caecum increased with development age. The pyloric caecum is clustered by multiple branches, each of which produces two sub-branches in the middle section. Ⅱ type of mucous cell was widely distributed in the pyloric caecum, followed by type Ⅳ, there was not Ⅰ type mucous cell. The amount of mucous cells on the base pyloric caecum were higher than the top part.