Abstract: The direct reduction process is an important development direction of low-carbon ironmaking and efficient comprehensive utilization of poly-metallic iron ore, such as titanomagnetite. However, the defluidization of reduced iron particles with a high metallization degree at a high temperature will seriously affect the operation of fluidized bed reduction. Coupling the pre-oxidation enhancing reduction and the particle surface modification of titanomagnetite, the behavior and mechanism of pre-oxidation improvement on fluidization in the fluidized bed reduction of titanomagnetite are systematically studied in this paper. Pre-oxidation treatment of titanomagnetite can significantly lower the critical stable reduction fluidization gas velocity to 0.17 m/s, which is reduced by 56% compared to that of titanomagnetite reduction without pre-oxidation, while achieving a metallization degree of >90%, Corresponding to the different reduction fluidization behaviors, three pre-oxidation operation regions have been divided, taking oxidation degrees of 26% and 86% as the boundaries. Focusing on the particle surface morphology evolution in the pre-oxidation–reduction process, the relationship between the surface morphology of pre-oxidized ore and the reduced iron with fluidization properties is built. The improving method of pre-oxidation on the reduction fluidization provides a novel approach to prevent defluidization by particle surface modification, especially for the fluidized bed reduction of poly-metallic iron ore.