Abstract: 【Objective】Understanding the structure characteristics of dominant tree species and their saplings during forest succession stages had an important role in forest restoration and forest management.【Method】On the basis of analysis on three forest types(poplar-birch secondary forest, spruce-fir mixed forest and spruce-fir near pristine forest)at different succession stages in Changbai Mountain, the important value and the univariate O-ring function statistic were used to analyze the dominance and spatial patterns of the main tree species and their saplings. 【Result】The numbers of adult tree were decreasing gradually with the succession,which was opposite to basal area. Pioneer species, such as Betula platyphylla, Populus davidiana, would disappear from the community gradually. Tree diameter distribution showed the reverse J-shape form in all types, most part of trees had small diameter at breast height(DBH)in poplar-birch secondary forest while trees with intermediary and large diameter dominated the other two types. Species of saplings were less and saplings for pioneer species rarely appeared, spruce-fir mixed forest had sufficient saplings with negative exponential distribution. The amount of sapling in secondary forest was the least, but basal diameter and height of saplings were significantly better than the other two types. Most of saplings in secondary forest were randomly distributed. However, saplings in spruce-fir mixed forest and spruce-fir near pristine forest were clumped significantly in 0-5 m scales, then they were distributed uniformly or randomly with scales increase. 【Conclusion】Poplar-birch secondary forest and spruce-fir mixed forest are in the process of positive forest succession, while the structure of the spruce-fir near pristine forest is unreasonable and the forest regeneration is poor. Measures like selective cutting should be taken to provide a more suitable environment for saplings and promote the process of forest succession.