Cracks, caused by shrinkage and external loading, facilitate the ingress of aggressive and harmful substances into concrete and indeed reduce the durability of the structures. It is well known that self-healing of cracks can significantly improve the durability of the concrete structure. In this research, self-healing of cracks was proposed to be realized by providing extra water for further hydration of unhydrated cement particles. In order to provide theoretical guidance for the practice, self-healing by providing extra water to promote further hydration was simulated. The simulation was based on water transport theory, ion diffusion theory and thermodynamics theory. In the simulation, self-healing efficiency under different conditions as a function of time was calculated. The relationship between self-healing efficiency and the amount of extra water from the broken capsules was determined. According to the results of the simulation, the amount of extra water can be optimized by considering self-healing efficiency and other performances.