Niche differentiation and habitat filtering are fundamental to species coexistence and biodiversity maintenance within forest communities. The highly complex crown structure of forest communities can be seen as direct partitioning within spatial niche dimensions. However,few studies have directly assessed the contribution of crown complementarity to biodiversity of forest communities. In this study,by using community survey data combined with tree individual crown data from a 1 hm² dynamic monitoring plot in 2023,we evaluated the effects of crown complementarity and topographic factors on the diversity of the Nanshan deciduous broadleaf forest community in Wucheng,Zhejiang Province. The results showed that: (1) Increased crown complementarity enhanced species diversity and tree height variation,and also made the deep phylogenetic structure more divergent,indicating that crown complementarity reflected the vertical niche differentiation of forest community,and tended to participate in the construction process of phylogenetic structure in the long-term historical evolution. (2) Elevation was the most important topographic factor influencing community diversity,showing negative correlations with both species diversity and structural diversity,leading to a clustering trend in phylogenetic structure. (3) Crown complementarity and topographic factors jointly influenced species diversity,phylogenetic diversity,and structural diversity in forest communities. Crown complementarity accounted for 43.24%,31.22%,50.16%,49.84%,and 53.60% of the explainable variance in the Shannon-Wiener index,Pielou's evenness index,Net Relatedness Index (NRI),Nearest Taxon Index (NTI),and coefficient of variation of tree height,respectively. However,its contribution to the explainable variance in DBH coefficient of variation was only 0.30%. In sum,we found that the increase of crown complementarity in Nanshan deciduous broadleaf forest is beneficial to the maintenance of community biodiversity. Our study suggests that including canopy complementarity in assessments of the effects of biotic and abiotic factors on biodiversity in forest communities can deepen our understanding of the mechanisms of biodiversity maintenance.