The anatomical structure characteristics of vegetative organs of wetland plant Acorus calamus were observed by the paraffin method and tissue segregation process, and the relationship between these structure characteristics and ecological adaptability of A. calamus was also discussed. The experimental results showed that A. calamus rhizome had adventitious roots. Radical epidermis was composed of a layer of cells, arranging compactly. The cortex was composed of the multilayer parenchymal cells, which were ruptured to form numerous aerenchyma. The endodermis had the thickened casparian band with horseshoe in cytoderm. The vessel column had 5 prototype primary xylems and 4—10 large-scale vessel to form the developed aerenchyma. The epidermis cells out of the rhizome were squared. The extine was thickened. The elementary tissue approximating to the epidermis had the sclerenchyma cell groups. The cortex parenchymal cells were arranged in chains. There was the large aerenchyma in the middle. The endodermis formed the Casparian strip. Lots of vessels were attached around the Casparian strip. Vascular bundles were scattered in the ground tissue. The central cylinder’s vascular bundle was presented in the amphivasal type. Partial region of rhizome was mutualized with endophyte to form nodulation. The leaves of A. calamus were isolateral. The parenchymal cells of mesophyll tissues were ruptured to form the large aerenchyma. The vein had the limited collateral vascular. There was a large vessel in the middle. The anatomical structure features of A. calamus showed that it was adaptive to the growth environment of wetland. A. calamus rhizome had the endophyte in nodulation, which could purify sewage. The developed adventitious root was suitable for division propagation.