Using the methods of parafine-mounted sectioning and staining by methyl green-pyronine and feulgen, the morphology and structure of midgut and silk-gland of silkworm, Bombyx mori, were observed by microscopy during metamorphosis. The experiment showed that there were a lot of amorphous cell-hke conglomeration inside the intestine. There were two ways which formed these conglomeration. First, old epithelium of midgut fell off into the intestine gradually while the regenerative cells on the base proliferated and formed into the new epidermic cell of papue. Second, parts of the old epidermis sank into the intestine and became the amorphous cell-like conglomeration, which was the main reason that the midgut shrunk increasingly. During the spinning, the material of silk decreased gradually and the bulk became lessening and thin. When the spin finished, silk gland changed remarkably, and the ectoblast of silkgland draped. There were increasing vesicles inside the cell of silk gland. Branch-liked nucleus changed into bunchs and then condensed into agglomerates. Finally, it degenerated and died out completely.