Abstract: The AFLP analysis of genetic diversity provided scientific basis for breeding and utilizing of the good varieties of Castanopsis fissa Rehd.et Wils. The genetic relationships among 39 Castanopsis fissa Rehd.et Wils’s half-sib families were analyzed by AFLP. The results showed that 8 pairs of primers produced 761 distinctive bands in total, 565 bands were polymorphic and the polymorphic rate was 74.14%, there were high genetic diversity among the different half-sib families. There were various genetic diversities among the different plus tree collection sites, the genetic diversity showed obvious regional character. There were different genetic diversity performances in the different collection sites: Hunan Tongdao, Fujian Mingxi and Guangdong Pingyuans’samples had low genetic variation. There were high genetic variations and genetic diversities in Guangxi Yongfu, Rongshui and Pingguos’samples. Cangwu’s samples had the highest genetic variation. The appearing chance of the excellent half-sib families of Castanopsis fissa Rehd.et Wils was closely related to the genetic diversity, the higher genetic diversity were, the more the excellent half-sib families appeared. The appearing chance of the excellent half-sib families had close correlated with the half- sib families′geographical position. The appearing chance of the excellent half-sib families had high reversely correlated with latitude and medium reversely correlated with longitude.