Abstract: “Algae” is a distinct group in modern plant classification systematics. Modern researches suggested that there were more than ten phyla in this group. However, the data on its history and its utilization by Chinese ancestors are poorly cared. The names and features related to “algae” were collected and sorted, and method of comparative morphology was employed to have a clear idea of“algae”. The research showed that there were ten plant names related to “algae” in the historical books and records of China, and eight of them were given a scientific name. Finally the understanding of Chinese ancestors on “algae” was analyzed. Medical value and edible value were the major reasons for the attention paid by Chinese ancestors.