This paper aimed to clarify the relationships among Wuyu， Arrowhead， and Water Chestnut in ancient works and give a theoretical support for subsequent relevant studies. We studied the phonology， botany， culturology， and philology， and believed that Wuyu in Han and Wei dynasties refered to Arrowhead. The reason for the name of Wuyu changed to Water Chestnut was mainly due to understanding of “Wu” character whose original meaning indicating bird has been transferred to color of black. Because of changes in name， some effects pertaining to Arrowhead had been shifted onto Water Chestnut. What’s worse， due to similar ecological environment and root character， toxicity or/and side effect in Iphigenia indica had been meant to Arrowhead. As far as food safety considered， it is necessary to set their relationships straight. It is said that Arrowhead has a great effect on clearing heat and tonifying with its rich nutritive components and great health-keeping value.