The understanding on the seasonal dynamics of the maximum net photosynthetic rate (A_max) and its nitrogen regulation in desert plants has been a concern in plant ecology. Understanding of the dynamics of A_max and its nitrogen regulation, especially the effect of leaf nitrogen allocation on the regulation mechanism of A_max is unusually limited in desert plants. In order to elucidate the mechanism of the seasonal variation in A_max in a dominant desert shrub, Artemisia ordosica. Seasonal variation in A_max and the effect of leaf nitrogen allocation on A_max were analyzed through season-long in-situ measurements of the light response curve (A-PAR), CO₂ response curve (A-Ci), leaf nitrogen along with simultaneously environmental measurements from May to October, 2018 in Mu Us Desert, Yanchi, Northwest China. As a result, A_max of Artemisia ordosica varied seasonally, being larger in the middle stage of leaf expansion, with a coefficient of variation (Cv) of 14%. The maximum value of photosynthetic nitrogen use efficiency (PNUE) was 11.82 μmolCO₂ gN ^-1 s^-1 in the middle stage of leaf expansion. At this time, the distribution proportion of leaf nitrogen in the photosynthetic system was the largest, and A_max had the maximum value of 29.48 μmol CO₂ m^-2s^-1. At the end of complete leaf expansion, the distribution proportion of leaf nitrogen in photosynthetic system (P_p) had a minimum value of 0.21. At this phenological stage, the plants had smaller A_max and lower photosynthetic capacity, and leaf nitrogen distribution was more inclined to non-photosynthetic system, which was beneficial to extend the life of plant leaves. The A_max was positively related to nitrogen content (N_mass), nitrogen distribution in light capture system (P_L), and nitrogen distribution in bioenergy system (P_b). P_L had the greatest directly positive effect on A_max(P<0.05), nitrogen distribution in carboxylation system (P_c) had indirect positive effect on A_max mainly through P_b, and P_b had the greatest explanation for A_max seasonal dynamics (R²=0.49, P<0.01). A_max of Artemisia ordosica was negatively correlated with leaf mass per unit area (LMA) (P<0.05), indicating that there were higher LMA and lower photosynthetic capacity when leaf photosynthetic rate was lower, and the mechanical toughness of leaves was stronger. The trade-offs between the seasonal variation of leaf nitrogen allocation, and leaf photosynthetic capacity and leaf structure traits, indicated an acclimation of a desert plant to its environmental changes in different phenological periods. The results would contribute to more realistic and accurate prediction of ecosystem response to changing climate, and to deepen understanding of photosynthetic acclimation to biotic and abiotic factors.