Abstract: This is an article in the field of ceramics and composites. Taking ilmenite ore as the research object, the possible phase transformation of FeTiO₃ in concrete liquid phase environment was analyzed in order to provide a basis for the utilization of ilmenite tailings. The thermodynamic stability of ilmenite (FeTiO₃) was analyzed by thermodynamic calculation. Ilmenite ore powder was soaked in simulated concrete pore solution at 20 ℃ and 80 ℃ for 28 d and 270 d, XRD and SEM/EDS were used to detect mineral transformation. Using ilmenite ore to replace part of the gravel to prepare concrete, the influence on concrete strength at 20 ℃ and 80 ℃ was studied respectively. The results of thermodynamic calculations show that FeTiO₃ is unstable in the environment of O₂ and converts into Fe₃O₄ or Fe₂O₃ and TiO₂. The immersion experiment of ilmenite in the simulated concrete pore solution shows that ilmenite has no obvious changes. The concrete strength test shows that at 20 ℃ and 80 ℃, when ilmenite ore replaces 5% crushed stone, the compressive strength of concrete increases, and when the replacement is 15%, the compressive strength decreases, the reason is that the quartz in the ilmenite ore has undergone an alkali aggregate reaction.