Abstract: To address environmental issues and decrease production costs, the disruptively innovative solidstate steelmaking process was investigated. In this process, a high-carbon sheet is continuously decarburized using an oxidizing gas to achieve a low-carbon sheet. A significant benefit of the process is the elimination of several conventional processes, including the basic oxygen process, secondary refinement processes, and continuous casting, and the absence of inclusions. The most important feature of the process is the use of high-carbon iron melts to avoid inclusion formation, so that secondary refinement processes are eliminated. To study the gas–solid reaction kinetics of the decarburization of Fe–C alloy strips in H₂/H₂O, the effects of the decarburization temperature, strip thickness, and decarburization time on the decarburization effect of the Fe–C alloy strips were studied by a controlled-atmosphere high-temperature tube decarburization furnace. The results show that prolonging the decarburization time, increasing the decarburization temperature, and reducing the strip thickness can improve the decarburization effect. The Fe–C alloy strip cross section is composed of the complete decarburization layer, partial decarburization layer, and nondecarburized layer at 1353 K. The microstructure of the complete decarburization layer is ferrite. The partial decarburization layer is composed of ferrite, cementite, and a small amount of graphite phase. The nondecarburized layer is composed of pearlite and a large amount of graphite phase. The thickness of the decarburized layer has a good linear relationship with the square root of the decarburization time, which can be described by the function y = kt^0.5. The diffusion activation energy of the decarburization reaction of the 1.5 mm Fe–C alloy strip is 122.36 kJ·mol⁻¹. The variations of the average carbon content were studied, and the apparent activation energy of the decarburization reaction of the Fe–C alloy strips was 153.79 kJ·mol⁻¹.