Abstract: The seedling morphology and anatomy of Trigonobalanus doichangensis are dealt with. The results showed that Trigonobalanus, Fagus and Nothofagus are much more closely related and they are rather different from the other genera of Fagaceae. Based on the seedling characters,we suggested that Fagaceae is divided into two subfamilies, in which Fagoideae only includes three genera:Trigonobala:Trigonobalanus,Fagus and Nothofagus,and this subfamily is a primitive taxon in Fagaceae.