Abstract: Peanut and sesame are important oil crops in China, and they play an important role in national production. In alkaline soils, iron deficiency and chlorosis often occur in single-cropped peanut; however, iron deficiency rarely occurs in single-cropped sesame. Iron deficiency symptoms in peanut are significantly improved when intercropped with sesame and have significant yield advantages and economic benefits. To explore the mechanism of improvement in iron nutrition of peanut in peanut/sesame intercropping system (peanut||sesame), a field experiment was conducted to investigate the effects of two intercropping modes of peanut and sesame with rows ratios of 4∶2 (P||S 4:2) and 6∶3 (P||S 6:3) on the leaves SPAD value, pH of rhizosphere soil, active iron contents and total iron contents of different parts, and iron accumulation and distribution per plant of peanut. In this experiment, peanut cultivar ‘Keda Heihua 001’ and sesame cultivar ‘Yuzhi No. 8’ were used as the materials, and peanut single cropping (SP) was used as the control. Furthermore, the yield advantages of two planting patterns of peanut||sesame were analyzed. The following results were obtained when intercropping was compared with SP: the leaf SPAD values of peanut in P||S 4:2 and P||S 6:3 treatments increased by 13.60%−30.10% and 22.15%−33.31% (P<0.05), respectively. The pH of the rhizosphere soil decreased significantly at the flowering and needling, pod setting, and pod expansion stages. Compared with those of SP, the contents of active iron in peanut stems and leaves were enhanced by 31.80%−72.78% and 24.41%−72.49% (P<0.05), respectively; and the total iron contents were enhanced by 16.80%−22.86% and 15.91%−27.88% (P<0.05), respectively, in P||S 4:2 and P||S 6:3 treatments. In addition, the iron accumulation per plant was increased by 7.91%−22.42% and 5.77%−15.58% in P||S 4:2 and P||S 6:3 treatments, respectively, at flowering and needling, pod expansion, and harvest stage; and, especially at harvest stage, the difference reached significant level (P<0.05). Compared with those of SP at the harvest stage, the total iron contents of peanut seeds in P||S 4:2 and P||S 6:3 treatments increased by 21.97% and 17.42%, respectively (P<0.05), and the yield advantage of peanut||sesame was P||S 6:3 > P||S 4:2. In conclusion, peanut||sesame can significantly increase the active iron contents in different parts of peanut, promote iron absorption and utilization, and improve the iron content and accumulation in seeds, and this is closely related to the fact that intercropping can significantly reduce the rhizosphere pH of peanut. The best intercropping pattern for iron nutrition improvement in peanut seeds was P||S 4:2; however, P||S 6:3 produced the highest yield.