Two batches of long time immersion tests of mortar specimens in sulfuric acid were carried out, in which the specimens with water cement ratio ranging from 0.5 to 0.7 were socked in sulfuric acid of pH value 1.5 to 4.0. The pH meters were used to monitor the pH changing of the soak solution. Sulfuric acid with concentration of 0.125 mol/L was added to maintain the original pH value of the solution and then acid consumption of specimens were recorded. Based on concentration boundary layer theory, a theoretical reaction rate model was proposed. The regression analysis of experimental data through theoretical model indicates that except for the pH value ranging from 2.3 to 3.5, the theoretical model can fit the experimental data well.