Abstract: Based on thermodynamic analysis, the production mechanism and path of iron carbide deoxidized from iron ore in fluid bed were studied. The results show that (1) ferric oxides are deoxidized according to the theory of Gradual Deoxidizing at 700°C, and iron carbide comes from the infiltrating reaction of CO; (2) iron carbide comes mainly from the reaction of FeO to CO with partly from the reaction of metallic Fe deoxidized from iron ore to CO at 586°C to 628°C; (3) when the temperature is lower than 586°C, iron carbide in product sample comes mainly from the reaction of Fe3O4 to CO, and the content of magnetite is higher correspondingly. By means of Mossbauer spectrum and X-ray diffraction, the phase analysis we made verified that iron carbide exits in product sample. All the results here will lay a theoretic foundation for industrial production of iron carbide.