Abstract: The steel corrosion of reinforced concrete under the mixture solution of sulfate and chloride is investigated. The effects of flexure loading on steel corrosion is discussed in this paper. Electrochemical methods are used to analyze the corrosion state of steel in concrete, the degree of corrosion is reflected with corrosion potential and corrosion current density. According to the hoop tensile stress at the outer edge of the rupture place induced by corrosion production, the damage degree of concrete(Ds) caused by steel corrosion is defined. The relation of the damage degree, corrosion current density and corrosion time-varying is established, which reflects the process of damage evolution. And the model verification is carried out.