An analytical model was developed to predict the tensile behaviour of a corroded steel bar. The model was established based on cross sectional analysis and was validated using experimental data for slotted steel bars and electrochemically corroded steel bars. The model was further used to predict the tensile behaviour of a corroded steel bar. The corrosion mode of the steel bar was supposed to be pitting corrosion and the distribution of the corroded section was supposed to follow a lognormal distribution. A power law between the parameters of the lognormal distribution and the average corrosion rate of the steel bar was used to predict the statistical distribution of the cross section area of a corroded steel bar. Based on these assumptions, the yield strength, ultimate strength and ductility of a corroded steel bar were predicted with different corrosion rates. The predicted behaviours are compared to collected experimental results from various sources. It is found that the numerical results of yield strength and ultimate strength agree well with the collected experimental results. The model slightly underestimates the ductility of the corroded steel bars. The result of the model would be helpful for the prediction of the tensile behaviour of reinforced concrete member subjected to chloride induced corrosion.