Abstract: Research photosynthetic characteristic variation of different families of Cyclobalanopsis gilva, providing theoretical basis for family selection and heredity resources conservation. Test materials were 1 year’s Cyclobalanopsis gilva, seedling about 7 families. Study the differences about photosynthetic characteristic of families. The results indicated: Among the families seedling, the Pn, Chl, Gs and Tr had significant differences. Gs, Tr were significant correlation with Pn. Pn was significant negative correlation with Ci. The photosynthetic characteristic among families existed significant hereditary variation. Gs maybe the key factor. In the selecting families, the 6th was the best.