Abstract: The changing pattern of tree species diversities in gaps at different developmental stages of evergreen broad-leaved forest in Mountain Wuyi was analyzed in this paper．The results show that the tree species diversity indexes in gaps are larger than that in non-gap stands，but the ecological dominance shows the opposite discipline．The tree species diversity indexes are changed in expanded gaps of different sizes and reach the highest in those with a size smaller than 100 square meter，but reach the lowest in the expanded gaps with a size larger than 300 square meter．Species richness，species diversity indexes and mean degree indexes of the species higher than 1．5m show a general trend with the development of gaps．reaching the highest level in the gap ages of about 10-20 years，but the lowest level in first ten years．The tree species diversity indexes and mean degree indexes in regeneration layer of gaps are decreased in the first 10 yea rs，reaching the lowest level in 10～20 years after gap formation，and then are increased in the next 30 years，reaching the largest level in 40～50 years，but a slow trend of decrea sing after 50 years after gap formation Gap formation provides the power for regeneration of tree different species．In order to preserve the species diversity，it is very important to make gaps in a proper way in forest production.