Based on field survey data of three 52 hm² permanent monitoring plots of coniferous and broad-leaved mixed forest in Changbai Mountain, the tree species with diameter at breast height (DBH) ≥ 1cm were used as the research object. R4.0.3 software was used to calculate the species diversity index and perform species diversity correlation analysis and multiple regression analysis to explore the impact of biotic and abiotic factors on the species diversity of coniferous and broad-leaved mixed forest at different succession stages. The results showed that:(1) the four species diversity indexes of the three typical coniferous and broad-leaved mixed forests decreased with the positive succession, among which the species richness, Shannon-Wiener index and Simpson index showed significant differences in the three succession stages, while the Pielou evenness index showed no significant difference in the secondary poplar-birch forest and the secondary coniferous and broad-leaved mixed forest. (2) The DBH structure variable was the main driving factor affecting the change of species diversity. With the succession, the impact of forest stand density on species diversity was increasing. (3) All soil factors showed significant indigenous effects on the species diversity index in the coniferous and broad-leaved mixed forest stage, while only soil total nitrogen had significant indigenous correlation with the species diversity index in the secondary poplar-birch forest. Soil total phosphorus was the main factor affecting species diversity at the stage of the mixed Tilia and Korean pine forest. In summary, the study concluded that in each succession stage, biotic and abiotic factors affected the species diversity of the forest communities. DBH structure and stand density are the main factors affecting the species diversity of the community, and the soil factors in the forest stand are affected by different community characteristics and produce different changes, which have different impacts on the species diversity of the community.