A systematic study was conducted on the influence of preparation conditions of caustic starch on the reverse flotation desilication effect of a certain Anshan style hematite ore in Hebei province. Through single-factor variable tests and closed-circuit process test, the optimization combination scheme of key preparation parameters such as causticity ratio, causticity temperature, and causticity time was clarified. The results show that under the optimal conditions of a causticity ratio of 8 : 100, a causticity temperature of 90 ℃, and a causticity time of 30 min, the selective inhibition performance of caustic starch was significantly improved. In the closed-circuit test, the iron grades of iron concentrate and tailings were 67.02% and 20.65%, respectively, with an iron recovery rate of 87.63%. Infrared spectroscopy and Zeta potential analysis revealed the mechanism of changes in the molecular structure and adsorption properties of caustic starch. The results confirmed that after causticization treatment, starch can effectively expose its hydroxyl and carboxyl groups, which enhances the chemical adsorption ability of the inhibitor on the surface of hematite, thereby achieving selective inhibition of hematite. The research result provides a novel approach for the green and sustainable development of the reverse flotation desilication process for hematite.