We have studied on the relation between the change of serum gastrin and the acute gastric mucosal lesion. Experimental result shows that the acute gastric mucosal lesion is related to the change of serum gastrin. When the acute gastric mucosal lesion of rats was induced by indomethacin, the serum gastrin level was increased obviously. The drug crude riboflavin preparation could decreased the release of serum gastrin caused by indomethacin.