Existing sulfate attack model of cement concrete cannot truly reflect the actual construction of cement concrete. Based on the existing sulfate attack model of cement concrete, effective sulfate diffusion coefficient under fatigue load was introduced to analysis the effect of different parameters on the sulfate corrosion life under fatigue load. Based on the analysis of the law, a practical formula for the sulfate corrosion life of cement concrete under fatigue load is established by a large number of uniform design calculations.