Abstract: This paper explores the characters of gap edge effect of the forest communities in Jinyun mountain. The species diversity and ecological dominance as well as the index of the edge effect of 29 forest gaps in Jinyun mountain are measured, on the basis of Shannon-Wiener index and Simpson index as well as the index of the edge effect. The results show that three indexes have an effect on explaining the gap edge effect in forest communities. Based on the measurement of the species diversity, the index of the gap edge effect in subtropical forest communities is about 1—3, and on the basis of the ecological dominance index, the former result is about 0.1—1.2, the results also show that the index of gap effect of forest communities is affected not only by its size, but also by its aspect and growing phase. The importance of gaps for regeneration of trees and maintenance of species diversity as well as the application of the gap edge effect on forestry practice are discussed.