Qiandao Lake was formed in 1959 when the Xin′’anjiang Hydroelectric Plant was built. There are 1078 islands with the area larger than 2500 m2 and many smaller islands. Potential vegetation of this area was dominated by evergreen broadleaved species. When the Plant was built, the vegetation was clear-cut and now vegetation on islands was dominated by Pinus massoniana, a pioneer species. However, pure pine vegetation is low in ecosystem service and apt to disease, such as Dendrolimus punctatus and pine wood nematodes. Therefore there is a need to restore potential vegetation, i.e. evergreen broadleaved forest. Previous surveys indicated that on some islands, there are some evergreen broadleaved species remaining, and Castanopsis sclerophylla is the most common one. We investigated the population structure of C. sclerophylla to reveal whether it can sustain on islands and to provide suggestions on ecological restoration. C. sclerophylla can be found on islands higher than 105.4m, while the highest water level of Qiandao Lake was 108.2 m. Number of individuals on islands, with a range from 4 to more than 4000, were significantly related with the areas or altitudes of the islands. Population structure indicated that, at genet level, C. sclerophylla on large and most medium-size islands could be self-sustainable, while on small and some medium-size islands C. sclerophylla could not be self-sustainable and will be decline. However, at the ramet level, almost all the C. sclerophylla populations, no matter on large, medium or small islands, seem to be self-sustainable. Further analysis indicated that resprouting contributed more than 81.6% of the genets and 94.8% of the shoots reproduced after the creation of the Lake. Above results indicated that, although small population size on some islands, these populations might be sustain via vegetative reproduction, especially resprouting, for a long period under the present situation without human’s disturbance and dramatic environmental changes. Conditions of most islands meet the surviving and growth of C. sclerophylla. Therefore, lack of seed or seedling is the main limit of the ecological restoration of evergreen broadleaved forests on islands of Qiandao Lake. However, no individual reproduced from sexual reproduction on some medium and small islands indicated that environmental condition might be another limiting factor of restoration.