Bayan Obo iron ore is a rare complex deposit in the world. An isothermal kinetic study of the mineral phase transformation process of hematite in suspension to magnetite in Bayan Obo iron ore was carried out. It was calculated that in the reduction process of the H₂ atmosphere, E_α was 99.87 kJ/mol and lnA was 13.07 min^-1. In the reduction process of CO atmosphere, E_α was 37.06 kJ/mol and lnA was 3.40 min-1. The reduction paths of Bayan Obo hematite under different reducing atmospheres are not the same: (1) H₂: hematite-magnetite-iron; (2) CO: hematite-magnetite-wüstite-iron. Under a CO atmosphere, the magnetic properties of the wüstite produced by the over-reduction of hematite were too weak, which seriously jeopardizes the magnetism of the reduced products. The pore structure was enlarged during the reduction of hematite, which greatly reduced the internal diffusion resistance of the reaction and accelerated the reaction rate.