Abstract: This study investigated the effects of different nitrogen fertilizer application ratios of base to topdressing on the nitrogen use efficiency, leaf senescence characteristics, and cotton yield under different planting patterns with the aim of providing a rational fertilization strategy for high-yield and efficient cultivation of cotton in Xinjiang cotton-growing areas. The cotton variety ‘Xinluzhong 84’ was chosen as the research object, and field experiments were conducted in Hailou Town, Shayar County, Xinjiang, in 2022 and 2023. A split-plot design was employed, involving two main planting patterns: one film with six rows with an alternating wide/narrow rows-spacing of 66/10 cm and plants-spacing of 12 cm (M6), and one film with three rows with an equal rows-spacing of 76 cm and plants-spacing of 6 cm (M3); and four nitrogen fertilizer application ratios of base to topdressing of 0∶0 (CK; no nitrogen application), 0∶10 (N0), 2∶8 (N2), and 4∶6 (N4) as subplots. There were totaling eight treatments. The total nitrogen application rate for all nitrogen treatments was 320 kg∙hm⁻². The nitrogen metabolism-related enzymes activities, leaf senescence-related enzymes activities, nitrogen use efficiency, yield, and yield components were measured. Results showed that in 2022 and 2023, the yield of seed cotton was higher in the M3N4 treatment, reaching 7 342.59 and 8 085.19 kg∙hm⁻², being 12.05% and 6.18% higher than those of the M6N2 treatment (optimal yield treatment of M6 pattern), respectively. Compared with that of the M6N2 treatment, the number of bolls per plant of the M6N2 treatment increased by 10.17%; however, the weight per boll decreased by 1.48% on average. The M3N4 treatment maintained a high activities of enzymes at the full flowering and boll stages, promoted nitrogen metabolism in cotton, and prolonged the functional period of cotton leaves. Compared with that of the M3 pattern, the maximum nitrogen accumulation rate (V_m) of the M6 pattern was increased; however, the occurrence time (T) of the maximum nitrogen accumulation rate was slightly delayed, the duration of rapid growth (∆t) decreased by 3.85–11.64 days, and the growth characteristic value (T_G) of the nitrogen growth period decreased by 4.23%–27.60%. The total nitrogen accumulation of cotton plants in each nitrogen fertilizer treatment under the M3 pattern was higher than that of the corresponding nitrogen fertilizer treatment in the M6 pattern, and the nitrogen accumulation in vegetative organs in the M3N4 treatment was significantly higher than that in the other treatments. Compared with those of the M6N2 treatment, the agronomic nitrogen use efficiency, nitrogen recovery efficiency, and partial factor productivity of cotton in the M3N4 treatment increased by 7.77%, 10.56%, and 8.90%, respectively; however, the physiological use efficiency of nitrogen fertilizer decreased by 3.03%. Reasonable nitrogen base-topdressing ratio and planting pattern can regulate the differences between individual and group cotton plants, increase the nitrogen metabolism levels and nitrogen accumulation and transport in various plant organs to enhance the nitrogen use efficiency, boost the physiological enzyme activity to delay leaf senescence in cotton plants, maintain a higher number of bolls per plant, and fully exploit the cotton production potential. Under these experimental conditions, a planting pattern with an equal spacing of 76 cm and a nitrogen fertilizer application ratio of 4∶6 was identified as optimal for increasing the yield.