In order to reveal the differences in the plastic responses of fine root stoichiometric traits to nitrogen addition between different mycorrhizal tree species, two tree species, Castanopsis faberi (ectomycorrhizal) and Schima superba (arbuscular mycorrhizal), were selected in an evergreen broad-leaved forest of Wanmulin Nature Reserve, Jianou City, Fujian Province. Root bag method was used to carry out the nitrogen addition experiment. The stoichiometric traits (C, N, P, C/N, N/P, and C/P) were measured after the fine roots have grown in the root bag for half a year. The results showed that root order had a significant effect on the stoichiometric traits of fine roots. With the increase of root order, the C concentration, C/N, and C/P of fine roots of C. faberi and S. superba increased significantly, while the concentrations of N and P decreased significantly. Nitrogen addition had a very significant effect on the concentrations of fine root C and N, but had no significant effect on the concentration of fine root P. As a result, the fine root C/N remained stable, but both N/P and C/P increased after nitrogen addition, indicating increased P limitation in fine roots. There was no difference in the plastic responses of fine root stoichiometric traits to nitrogen addition among different root orders, and between ectomycorrhizal (C. faberi) and arbuscular mycorrhizal tree species (S. uperba) as well. It is concluded that the fine root stoichiometric traits of arbuscular mycorrhizal and ectomycorrhizal tree species had similar responses to N addition in this study.