Abstract:Using the contiguous grid quadrats, the population structure and distribution pattern of Celtis sinensis from Fangshan National Geology Park in Nanjing were studied. The results showed that: (1)The size class structure of the population was basically the same, i.e. the seedlings number of Ⅰ and Ⅱ classes was less, hence, the young seedlings reservoir was very few. The individual distribution of population was focused at Ⅲ and Ⅳ classes, the number over Ⅳ class reduced gradually. (2)From the static life table of the population, it was found that the mortality of Ⅰ and Ⅱ classes was negative because the seedlings number of Ⅰ and Ⅱ classes was less, and the mortality of Ⅶ and Ⅷ classes was the most. In most of the populations, the young trees were too few to provide enough recruitment, resulting in the ageing phenomena, and the population was declining. (3)The spatial pattern of seven sampling plots showed aggregative distribution through testing the cluster-intensity coefficient for instance K-value of negative binomial, dispersal index (C), index of dispersion pattern (Iδ), Cassie index (Ca), clumping index (I), index of mean crowding (m*) and index of patchiness (m*/m), but there were certain differences among seven sampling plots about their aggregative degrees.