Abstract: Genus Chaydaia only includes 1 species—Chaydaia tonkinensis Pitard, while Chaydaia rubrinervis (Levl.) C. Y. Wu ex Y. L. Chen is identified to be a new synonym. Genus Chaydaia distributes to the south of the Miaolin Mountains in the Southwest and Hainan Province in China, Vietnam, Philippines, and Thailand, in which it is a new record. Its original area, period, and migration line are discussed as well.