Cr modified alloy steels using HRB400 steel as base alloy were produced by remelting in a vacuum. Their corrosion resistance were estimated by open circuit potential, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy and immersion test in saturated Ca(OH)₂ simulated concrete pore solution. The modified alloy steels exhibit higher corrosion resistance with a high chloride thresholds, lower corrosion current density and higher impedance than HRB400 steel rebar. Cr can modify the proportion of Cr element in the passive film. The immersion test showed that the new alloy steels have lower corrosion rates. The new alloy steels have longer durability than HRB400 steel.