Based on the thickness of surface corrosion layer and the loss rate of compressive strength in corrosion region and according to the model of strength damage of corroded concrete, the test of three groups of concrete samples immersed in sodium sulfate solution for long time was carried out. The experimental results were fitted, and parameters were analyzed. It is revealed that the calculation results and test results are in good agreement. The results show that the concrete under sulfate environment may be divided into three regions： expansion dense region, crack development region and uncorroded region. The comprehensive corrosion coefficient may reflect relationship between concrete mix ratio and corrosion resistance, the higher the corrosion coefficient, the worse the corrosion resistance. According to the model of strength damage of corroded concrete and the computation method of corrosion resistance coefficient for compressive strength, concrete corrosion resistance under sulfate environment may be evaluated and forecasted.