The drought caused by global climate change and the increased atmospheric nitrogen deposition caused by human activities will directly affect the structure and function of forest ecosystems. Leaves and fine roots are the most important resource-obtaining functional organs of plants, whose stoichiometry characteristics can indicate their resource utilization and survival adaptation strategies. Under the background of climate change, understanding the stoichiometry and adaptive characteristics of plants will be beneficial to predict future changes in the forest's ecosystem functions. Through a two-factor interaction experiment for one year, this study explored the response characteristics of the stoichiometry ratio of carbon (C), nitrogen (N), and phosphorus (P) elements in leaves and fine roots of Moso bamboo (Phyllostachys edulis) forest (an important subtropical forest type in China) under the dual influences of throughfall reduction and nitrogen addition. It is of great significance for understanding the adaptation of Moso bamboo forest ecosystem to global changes and nutrient utilization strategies. The results showed that (1) the throughfall reduction significantly decreased N and P contents in leaves, but significantly increased N content in fine roots, and had no significant effect on C content in leaves as well as C and P contents in fine roots. Nitrogen addition significantly increased N content of soil and N content in leaves, but had no significant effect on C, P contents in leaves and C, N, P contents in fine roots. (2) The throughfall reduction, nitrogen addition and their interaction had no significant effect on the ratio of C:N:P of soil. (3) The throughfall reduction significantly increased the ratios of C:N, C:P, and N:P in leaves. Nitrogen addition significantly decreased the ratio of C:N in leaves, but had no significant effect on the ratios of C:P and N:P in leaves. The interaction of throughfall reduction and nitrogen addition significantly decreased the ratios of C:N and C:P in leaves, but had no significant effect on the ratio of N:P in leaves. (4) The throughfall reduction significantly decreased the ratio of C:N in fine roots, but had no significant effect on the ratios of C:P and N:P in fine roots. Nitrogen addition and the interaction of throughfall reduction and nitrogen addition had no effect on the ratio of C:N:P in fine roots. Our study indicated that Moso bamboo adopted strategies to reduce N and P contents in leaves, increase N content in fine roots, improve N and P utilization efficiency in leaves, and maintain fine roots' stable P utilization efficiency. Nitrogen addition failed to alleviate drought stress caused by the throughfall reduction on Moso bamboo. Moso bamboo coped with drought stress through changed N distribution pattern and N, P utilization efficiency between the aboveground (leaves) and the underground (fine roots). Under the treatment of nitrogen addition, N content in leaves increased significantly, and the ratio of C:N decreased significantly. However, C, N, and P contents in fine roots as well as the stoichiometric ratio did not change significantly. It can be seen that the aboveground (leaves) and the underground (fine roots) of Moso bamboo have different response strategies to the throughfall reduction, nitrogen addition and their interaction. This study can provide theoretical basis for the sustainable management of Moso bamboo plantation under the background of global change.