Underground rhizomes of Fargesia yunnanensis from different ages were used as experimental materials in the study. They were observed under the light microscope byroutine section method, then their anatomical structure characteristics and dynamic changes in anatomical features with ages were analyzed, in order to provide new data information of anatomy for their structural study. The main results were as follows: (1) in an underground rhizome internode, there is only one layer of cells in the epidermis. The hypodermis is composed of 3-4 layers of fiber with thickened cell wall. The cortex generally has 20-25 layers of irregular parenchyma cells, which form air way cortexes when matured. The pith is solid without pith cavity. (2) The diameters of fiber cells wall increase as the increasing age of underground rhizomes, and inner phloem areas of underground rhizomes at the same age are larger than outer sides. The fiber lumens decrease with increasing age, while inner fiber lumens of underground rhizomes at the same age are larger than outer sides. The sizes of vascular bundles, phloem and vessels increase as the increasing age of underground rhizomes. (3) The protoxylem of vascular bundles generally has no vessel, and the metaxylem of outer vascular bundles generally has two larger vessels. However, in the middle and internal vascular bundles of the underground rhizome, there is usually only one vessel in the metaxylem, and the other metaxylem vessel is not developed or underdeveloped. (4) In the 0.5 to 2 year old underground rhizomes of F. yunnanensis, lignins dyed in purple are distributed in fiber cell wall, parenchyma cell wall and vessel cell wall, and the degree of staining increases with increasing age of underground rhizomes. This indicates that the content of lignin and the degree of lignification increase with increasing age of underground rhizomes.