Abstract: In 2006, 2011 and 2015, 1-year container Phoebe bournei seedlings were mix planted in Cunninghamia lanceolata plantation afforestated in 1989 in Kaihua, Zhejiang province. In June 2021, sample plots were established in above-mentioned three plantation and pure C. lanceolata stand and determination was implemented on their soil nutrient contents and stoichiometry of soil C, N, and P. The results showed that biomass of aboveground, root and litter in mixed plantations increased with the stand age, but the understory vegetation biomass decreased gradually. The contents of soil organic carbon, nitrogen and phosphorus also increased with stand age. The contents of soil organic carbon, total nitrogen and phosphorus in the 15-year mixed plantation increased by 55.4%, 83.9%, and 84.7% than that in the pure C. lanceolate plantation. Bulk density in mixed plantation decreased gradually with the stand age, while soil pH, ratio of C/N, C/P and N/P had a little change. The biomass of above ground stand and root had evident positive relation with soil organic carbon, total nitrogen, and total phosphorus.