Abstract: This study aims to test the phylogenetic structure of a secondary Populus davidiana-Betula platyphylla forest (PBF) for multiple-spatial scale and ranked diameter class in Changbai Mountains of northeastern China, for the purpose of understanding the underlying mechanism of forest community assembly. We built a phylogeny tree based on 47 wooding species whose DBH≥1 cm. The results showed that with the increase of spatial scale, the dispersion degree of phylogenetic structure first increase then decrease; and with the increase of diameter class, the phylogenetic structure changed to overdispersion trend. These results suggested that the community was influenced by the effects of competitive exclusion and the abiotic filtering. Specifically, in small spatial scale, the phylogenetic structure is mainly decided by the effects of competitive exclusion; while in large spatial scale, the phylogenetic structure is mainly decided by the effects of abiotic filtering. By decomposing phylo-beta diversity with spatial factors and environmental factors, we find that environmental factors are powerful in explaining phylo-beta diversity. Among which, soil moisture and soil depth are the key factors to interpret phylo-beta diversity variance.