Abstract: During July and September 2020, 138 sample plots with 20 m×20 m were established in the forest dominated by Quercus glauca in 9 cities of Zhejiang province, and woody plant with DBH ≥5 cm in the plots were recorded. The effect of species diversity, DBH and tree height on biomass of arbor layer was analyzed by structural equation model. The result showed that DBH, tree height and species diversity had direct and indirect effects on the biomass of the canopy layer. The direct effects are 0.17, 0.35, and −0.42, respectively, while the indirect effects through other factors increase the total effects by 64.71%, 20.00%, and 40.50%, respectively. The negative effect of species diversity was related to the dominant position of Qu. glauca.Uneven aged and multi-storied stand forestry management model is beneficial for fully utilizing the nutrient space within the forest and promoting the accumulation of biomass in Qu. glauca forests.