Abstract: Fiber reinforced concrete (FRC) is a complex heterogeneous composite material, and its macro durabi-lity will be determined by the microscopic and mesoscopic components. By electing representative elements, a multi-scale model was established in this study to predict the chloride diffusivity of FRC with the consideration of heterogeneous feathers from micro to macro scale. In the present model, the percolation effect and the interface transition zones (ITZs) between fiber, aggregate and cement paste were carefully considered. Taking basalt fiber concrete as an example, the model was verified by experimental data and the influential parameters were discussed in detail. The results show when the water to cement ratio (w/c) exceeds a certain limit (about 0.45), the chloride diffusivity of FRC increases exponentially with the w/c, and results also indicate that the chloride diffusivity of FRC is mainly affected by the ITZs between the fiber and the cement paste. Adding the fiber content or decreasing the diameter of fibers will all increase the volume fraction of ITZs and lead to a poor chloride resistance performance. However, it is interestingly to find that no fixed negative or positive relationship exist between chloride diffusivity of FRC and the fiber content. The proposed model can effectively predict the diffusivity of FRC and hope to provide guidance or reference for engineering practice.