Abstract: This study aimed to investigate the optimal nitrogen (N) application rate for the high-yield and high-quality cultivation of wheat and to enhance N fertilizer use efficiency. This study used ‘Zhengmai 1860’ as the material, four N application treatments were established: 0 (N0), 90 (N1), 180 (N2), and 240 kg·hm⁻² (N3). The effects of these N application rates on wheat photosynthetic characteristics, grain filling process, and yield composition were analyzed. The results demonstrated that nitrogen (N) application significantly influenced wheat photosynthetic characteristics, grain filling process, and yield formation. Appropriate nitrogen application significantly enhanced the efficiency of light energy capture and conversion by increasing the SPAD value and the activity of photosystem Ⅱ (PSⅡ) (F_v/F_m, maximal photochemical efficiency of photosystem Ⅱ, F_v/F₀, potential activity of photosystemⅡ, etc), thereby providing sufficient assimilates for grain filling. Based on the two-year average data, compared with the N0 treatment, the SPAD value in the N2 treatment increased by 16.82%, while the F_m (maximum fluorescence), F_v/F_m, and F_v/F₀ in the N2 treatment increased by 6.01%, 1.59%, and 10.08%, respectively. Based on the two-year average data, under the N2 treatment, the maximum grain filling rate (V_max), the time to reach maximum grain filling rate (T_max), and the duration of grain filling (T) of ‘Zhengmai 1860’ increased by 11.16%, 4.81%, and 5.68% compared with the N0 treatment, respectively, which further promoted the increase in grain yield. Additionally, the durations of the gradual increase stage, rapid increase stage, and slow increase stage of grain filling (T₁, T₂, T₃) and their corresponding average filling rates (V₁, V₂, V₃) were all the highest under the N2 treatment. The N2 treatment also resulted in the highest grain yield and 1000-grain weight: the yield was 41.15%, 14.05%, and 11.42% higher than that under the N0, N1, and N3 treatments, respectively. The study indicated that a nitrogen application rate of 180 kg∙hm⁻² on the alluvial soil in the Huang-Huai Wheat Region was the optimal rate for ‘Zhengmai 1860’ to achieve the coordinated optimization of photosynthesis, grain filling, and yield under the experimental conditions. This finding can provide a theoretical basis for nitrogen-efficient cultivation in the Huang-Huai Wheat Region.