Abstract: The corrosion behavior of Q235B hot-rolled H-beam steel under the combined action of iron oxide scale and corrosion inhibitor was studied by corrosion weight loss test, polarization curve and AC impedance test with SEM and XRD.The results show that the corrosion resistance of the iron oxide scale structure from low to high is Fe₃O₄+Fe＜FeO＜Fe₃O₄.Under the action of circulating water, the corrosion products are α-FeOOH, γ-FeOOH, β-FeOOH and Fe₃O₄. Under the action of the compound corrosion inhibitor, Fe₂WO₆ precipitation passivation film appears on the surface of the base steel, and there are insoluble Zn（OH）2and complex ZnOHCl with inhibited the occurrence of corrosion. In the two environments（circulating water and compound corrosion inhibitor）, the corrosion rate and self-corrosion current decreases first and then increases, and the minimum values are 0.2071 g·m^-2·h-1, 2.14 ×10^-5A·cm^-2and 0.1010 g·m-2·h-1, 1.81 ×10^-6A·cm^-2. The impedance modulus increases first and then decreases, and the maximum values are 720.6 Ω·cm²and 26554.2 Ω·cm².