How to explain the causations of the diversity and the rarity, and how to measure the relations reasonably between the species diversity and the community stability are still the controversial problems in the community ecology. MacArthur contributed the factors affecting community stability to the species abundance and the interactions inside the community. In 1990s, researchers including Doak put forward that the community population capacity and the maintain mechanism are the crucial factors influencing the community stability. At the same time, great advances had been achieved in the study on the structure and the maintain mechanism of the community. In 2001, Hubbell and other ecologists introduced a new neutral theory (Unified Neutral Theory of Biodiversity and Biogeography) to explain the species co\|existing in community; this theory provided a new quantifiable way to measure the relations between the species diversity and the community stability. This paper analyzed the dynamics model of the species abundance in local community according to Hubbell′s neutral theory based on the neutral hypothesis of the community theory, concluded that the ecological quantify relations between the species diversity and the community stability in neutral theory. Firstly, the time to extinction or mono\|dominance of the species is positively related with the community size and the relative species abundance in the isolated local community from meta\|community. Thus, the time to extinction or mono\|dominance of the species in the local community will be prolonged and the community stability will be improved when the community diversity increased. Secondly, in the local community that open to immigration from the meta\|community, the expected abundance of an arbitrary species is positively related with the local community size and its relative species abundance in the meta\|community. So the species extinction in the meta\|community will provoke the extinction of the same species in local community and finally will reduce the community diversity. The abundance variance is related with the local community size, immigration, and the relative species abundance in the meta\|community. So, the community stability will be improved with the decrease of the abundance variance while the ecology isolation is weakened or the community diversity is increased. Therefore, species diversity of the meta\|community is one of the factors affecting the species diversity of the local community, the decrease of the ecology isolation and the increase of the species diversity are factors affecting the community stability.