We explored the C, N, P stoichiometry of fresh leaf, leaf litter and soil in Eucalyptus grandis mixed plantation of Toona ciliate, Alnus formosana, Sassafras tzumu and E. grandis. The results showed that the N∶P ratios of fresh leaf, leaf litter and soil ranged from 6.7 to 9.7, 8.6 to 9.7, 1.6 to 4.0, respectively. For the same components above, the C∶N ratios were 29.6 to 62.8, 78.4 to 101.8, 15.3 to 19.5, and the C∶P ratios ranged from 279.9 to 459.3, 639.0 to 795.9, 24.9 to 77.6, respectively. Among the four tree species, S. tzumu had the highest C storage capacity and N, P utilization efficiency. The leaf litter C∶N and C∶P of the three associated tree species were lower than that of E. grandis, suggesting that the leaf litter of the associated tree species was more easily decomposed and the associated trees may accelerate N, P cycling rates in the mixed forest. According to the fresh leaf N∶P <10, we found that E. grandis mixed plantation was considerably limited by N element, and E. grandis was limited more seriously. There were significant differences of soil N, P contents and C∶N∶P among different tree species, indicating that N, P cycling of Eucalyptus grandis plantation could be changed by the introduction of associated tree species. Moreover, the benefits of associated tree species in mixed plantation ecosystem will increase with forest age.