Abstract: Fagaceae is one of the most important families in temperate and subtropical regions. There are 7 gena and about 352 species and variants in China. The distributions of species richness and species Endemic Index and their relationships with climatic and geographic characters of Chinese Fagaceae were studied. The Endemic Index is firstly defined in this paper to describe the speciality of species components in some flora. If there are N species in some flora, and the i-th species has been found in another Ki—1 flora,then the species Endemic Index(EI) is defined as follow:

EI=(N/∑Ki)×10