Nitrogen (N) and phosphorus (P) elements play key roles in the structure and function, stability, service value and sustainable development of ecosystems. However, since the industrial revolution, global climate change has been increasingly affected by human activities. Climate change differentially affects nitrogen (N) and phosphorus (P) cycles in arid and semi-arid regions, which results in changes in plant biomass accumulation and vegetation productivity. Revealing the mechanisms of plant biomass accumulation and allocation in arid regions for responding to nitrogen and phosphorus addition could enhance an understanding of vegetation strategies under N and/or P deposition resulting from climate changes. In this study, Caragana korshinskii Kom., one dominant taxa in the desert, was selected to elucidate the accumulation, distribution and allometric growth in aboveground/belowground biomass. The N addition included three fractions (NH⁴⁺, NH₄NO₃, NO₃^-) and P addition included one fraction, i.e., H₂PO^4-. They were all experimented with in four concentration gradients (4 g/m², 8 g/m², 16 g/m², and 32 g/m²). Results showed that there was no significant difference in C. Korshinskii biomass under the four concentrations of NO₃^-, the interaction of added concentration and time also had no significant effect on the biomass of C. Korshinskii; in contrast to NO₃^- addition, the interaction between NH₄⁺ concentration and time had a significant effect on the biomass of C. Korshinskii, and NH₄⁺ addition alone had a significant inhibitory effect on the growth of aboveground/belowground parts of C. Korshinskii; the NH₄NO₃ addition in the low concentration promoted the aboveground and belowground biomass of C. Korshinskii, but this promotion disappeared with the growth of C. Korshinskii or the increase of NH₄NO₃ concentration. The high concentration of NH₄NO₃ (32 g/m²) inhibited the growth of C. Korshinskii; the interaction of P addition concentration and time had no significant effect on the aboveground biomass of C. Korshinskii, but had significant effects on its belowground biomass. Low concentration nitrogen (4 g/m²、8 g/m²) atddition would preferentially allocate the biomass of C. Korshinskii to the aboveground, while adding phosphorus changed the biomass allocation strategy to the aboveground, which supports the optimal allocation hypothesis. In conclusion, the study results highlight that C. Korshinskii changes the strategy of biomass allocation to the aboveground/belowground for responding N or/and P deposition. This conclusion not only enhance an understanding of plant strategies but help us revealing N and P cycling and transforming between soil and plant in the arid area under global climate change.