Xishaungbanna tropical rainforest (XTR) is the most intact tropical rainforest in China, and is the only oasis at around 21 degrees north latitude. The purpose of this study was to explore the effects of nitrogen (N) exogenous input on ecological stoichiometry of soil and foliar, and to assess the impact on the ecosystem of XTR. The results showed that the N content and nitrogen:phosphorus (N:P) in soil of XTR were increased significantly in different levels of N addition, especially in the low N addition. The P content in soil and leaves was generally reduced or flat compared with those before N addition. Meanwhile, N:P of soil had a significant relationship with the N and P content after N addition. However, the correlated coefficient between N:P and N, P content of plant leaves was significantly reduced by the N addition, respectively. This indicated that the impact of N deposition on the XTR ecosystem is very significant. Therefore, increase of N deposition may intensify the limiting effect of P in ecosystems, and aggravate the patchiness and degradation of XTR ecosystem due to global warming.