Abstract: A comparative structure study of stem and underground stem between "gangchai" and "shachai" was carried on by us. At the same time, we observed the variation of fiber morphology in the ninth, fifth and second internodes of the stem respectively.The morphology and anatomy between "gangchai" and "shachai" are almost alike. The distribution of short cell on the epidermis of "gangchai" is little more, sometimes, they are get together into a colony. These categories are vice versa in "shachai". The density of short cell distribution on the upper, the most; the middle, the less; the lower, the least. In their cross sections, there is only one fiber layer inside of "gangchai" epidermis; but there are 2—3 fiber layers in "shachai". The "V" shaped vascular bundle is round or ellipsoidal in "gangchai" arranged into 5—6 wheels. The vessel number in its metaxylem is variable, the highest, 7—8; in general, 2—3. The vascular bundle of "shachai" is plate-rounded, arranged into 4—5 wheels The vessel number in its metaxylem is few, from two to three. There are several small vascular bundles differentiated inperfectly scattered in the center of pith on the upper internodes of stem. The structure of both stem and rhizome is almost the same.The fiber length of "gangchai" and "shachai" varies according to its possition on the stem, the longest, in the fifth internode; the shortest, in the ninth internode; the middle, in the second internode. But the length and the ratio of length to width in "gangchai" is larger one-third than that of "shachai". By the way, the stem of "gangchai" contains a few of non-fiber cell, its fiber quality and productivity in a unit area are better than those of "shachai" also.From the above analysis of morphology and anatomy, we believe that "gangchai" and "shachai" are probably originated from one species and this species has differentiated into two different varieties—"gangchai" and "shachai". In other words, we have to do some work about morphology and anatomy of their reproductive organ especialy about their cytology and embryology for the final identification.