Abstract: A new species of the genus Excoecaria (Euphorbiaceae), E.yuanjiangensis is described from Yuanjiang County, Yunnan Province. It is related to E.acerifolia, differing in leaves evergreen, nearly opposite, subleathery, petioles longer, stipules broadly triangle; inflorescences sturdy and long, flowers densely aggregated, bracts apex acute, glands on the base ventral surface, anthers reniform; fruit ribs obviously elevated.