Abstract: The ultrastructural changes during the developing process of Stevia rebaudiana Bertani has been observed.The "prolamellar bodies" in the bud etioplast consist of netted "lattice bodies" formed by tubules; the "plastid center" disperses gradually, forming radius arranged lamellar structure. The plastid envelope appears protruding gemma-like body,probably being a kind of plastid proliferation.After the young leafs having turned green, the dispersion of "plastid center" disappears, the thylakoid forms on the whole, and the "prolamellra body" transforms into lamellar structure.As the leaf grows green, grana lamella and stroma lamella are both differentiated apparently: grana lamella are being increasingly piled up,photosynthetic membrane systems are quite developed.In the young leaf and in the extending leaf-cell, the division of the chloroplasts can be observed, forming dump-bell shapes—the principal means of the proliferation of chloroplasts.