Abstract: The stress and deformation safety of the concrete slab is crucial to the concrete faced rockfill dams (CFRDs), however, most of the traditional methods do not consider the effects of the reinforcement in slab, therefore, the calculated results can not provide enough information to the design of slab reinforcement. In this study, a method for calculating the slab reinforcement based on the concept of crack width limit is proposed: the non-coordinated grid computing technology is used to refinedly simulate the stress of the concrete slab, the embedded steel element is used to simulate the reinforcement effects, and the damage model is used to simulate the cracking of the slab concrete. By introducing a formula for crack width related to geometric size and rebar stress, and setting the crack width limit, the reinforcement calculation is realized. The proposed method can be used to quantitatively study the slab reinforcement and provide a theoretical basis for reinforcement design under complex conditions. The Dashixia CFRD under construction is taken as an example and its slab reinforcement design is preliminarily studied.