Corrosion behavior of steel bar in concrete was investigated and a prediction model for corrosion rate was developed with commonly used engineering parameters based on theoretical analysis, numerical simulation and experimental validation. An improved model for concrete resistivity was proposed by fitting the experimental data first. Then the influences of water cement ratio, chloride content, cover depth and relative humidity on the control mode of corrosion process and the steel corrosion rate were investigated according to electrochemical mechanism and macro cell corrosion model. Finally, a prediction model for corrosion rate was proposed based on the nonlinear regression with commonly used engineering parameters. Analysis results demonstrate that the proposed model could reflect the variation trend of corrosion rate under both resistivity and cathodic control modes with desirable accuracy and practicality.