This paper describes the optimal design of ductile fiber reinforced cementitious composite (DFRCC) under fatigue loading. First of all, fatigue tensile experiments of the DFRCC under constant strain amplitude were conducted, and the degradation of bridging stress was measured. The test results were employed to verify the micromechanics-based theoretical model developed in this research. The model accounts for the loss of fatigue ruptured fibers of which fatigue rupture is based on S-N relationships. According to the parametric study from the theoretical model, we found that the optimal choice of design variables, such as fiber length, is varied according to the maximum strain level and the number of cyclic loading. Therefore, it is required to design DFRCC optimally under given loading conditions to make the most of its excellent material properties and the developed model enables such a design.