Compared with other processes, the direct reduction-magnetic separation process can achieve the removal of lattice phosphorus in the iron minerals of high-phosphorus iron ore. Compared with a single phosphorus removal agent, when using sodium carbonate and calcium carbonate as a combined phosphorus removal agent, it has the advantages of low dosage and good phosphorus removal effect. However, the intrinsic relationship between phosphorus transformation and iron mineral reduction has not been revealed. This paper studied the influence of calcium carbonate and sodium carbonate on the phosphorus reaction process. The results showed that the addition of calcium carbonate and sodium carbonate reacts with the silicon components in the high‑phosphorus sample to form calcium silicate, preventing the reduction of the apatite that has been formed. At a reduction temperature of 1200 ℃ and a reduction time of 5 min, the phosphorus in the iron minerals enters the gangue phase when the iron minerals are reduced to wustite, and prolonging the time further promotes the formation of metallic iron and the growth of metallic iron particles. This result provides a theoretical basis for the efficient utilization of iron minerals with lattice phosphorus.