Abstract: Experiments were conducted on interplanting of Cassia corymbosa with two densities (LD: 10 plants per m2 and HD: 40 plants per m2) in Camellia oleifera plantation with 6 years cultivation in Suichang, Zhejiang province during March and April 2020. Determination was implemented in October on the growth of C. corymbosa. The results showed that height growth of C. corymbosa in HD was significantly higher than that in LD (P <0.005), and it had significant difference in the biomass distribution between two densities. Under LD treatment, the proportion of root and fruit was 1.45 and 2.69 times of HD treatment, while the proportion of stem and branch was only 70.6% of the latter. There was larger leaf thickness, smaller leaf circumference, leaf area and specific leaf area under LD treatment (P<0.05). There was no significant difference in photosynthetic rate among different densities (P>0.05), but higher stomatal conductance, transpiration rate and intercellular CO2 concentration in HD treatment (P < 0.05).