To explore the effects of leaf nitrogen (N) and phosphorus (P) on biomass relative growth rate (RGR) and to test the growth rate hypothesis (GRH) of plant ecological stoichiometry, two stands (9- and 13-year-old plants, respectively) of Machilus pauhoi were selected. The leaf nutrient contents (C, N, P) and biomass RGR were measured at different growth periods. The results showed that the stand age had significant effect on RGR and leaf C, N, P stoichiometry. Specifically, leaf nitrogen contents were significantly correlated with leaf phosphorus contents within the two differently aged M. pauhoi stands. Quadratic correlation was observed between the RGR and leaf P content, C : P, and N : P ratios in 9-year-old stand. In contrast, growth rates were linearly correlated with leaf N and P stoichiometry in 13-year-old stands. Studies had shown that in the environment that meets the needed plant nutrition, leaf N and P showed a positive linear correlation with the relative growth rate of trees; however, when the nutrient content in the environment was inadequate for the fast plant growth, the plants underwent adaptive adjustment to the limited nutrient resources.