Histological and Histochemical studies on digestive system of Mytilus edulis were reported in this paper. The digestive system of Mytilus edulis consists of digestive gland and digestive tract-esophagus, stomach(including style sac), intestine and rectum. The digestive gland is a compound tubular gland having two kinds of cells:digestive cells and basophilic cells. The wall of the digestive tract is made of three layers:tunica mucosa, tunica submucosa and tunica serosa, no muscular layer. Most of the epithelia are ciliated columnar cells. Histochemical studies show the basophilic cells in the gland contain abundant protein and RNA. The digestive cells contain lipid and many kinds of enzymes:non-specific esterase,acid phosphatase, proteinase, lipase and alkaline phosphatase. But the kinds and the activity of enzymes are less and weaker than that in the digestive gland.