Based on experiments on concrete specimens subjected to fatigue loading, the applicability of the three- stage deformation law and the invariance of the critical strain in the second stage are inspected. It is demonstrated that the three-stage law is universally applicable and has nothing to do with concrete strength and load form, and that the invariance of the critical strain in the second stage is only suitable for concrete materials with the same strength grade and has nothing to do with the loading history. A formula for calculating the fatigue life is put forward based on the above deformation laws, and the formula can be used to predict the residual fatigue life of existing concrete structures.