The rib-to-deck detail in orthotropic steel bridge deck is one of the details that are prone to fatigue damage in steel bridges. In engineering, the method of bonding carbon fiber reinforced polymer (CFRP) is commonly used to reinforce fatigue cracks at the detail location. In order to study the effectiveness of CFRP reinforcement for the rib-to-deck detail of orthotropic steel bridge deck and analyze the long-term durability of the adhesive layer between steel and CFRP, a multi-scale finite element model of the orthotropic steel bridge deck segment was established using ABAQUS finite element software. The extended finite element method was employed to simulate the fatigue crack at the weld toe of the rib-to-deck detail, and the variation in the stress intensity factor at the crack tip before and after applying CFRP was calculated. Based on the linear cohesion model theory, a cyclic cohesion model considering the cumulative process of adhesive layer interface stiffness degradation was derived, and the corresponding subroutine was compiled to simulate the damage evolution behavior of the adhesive layer interface under cyclic loading. The research results show that CFRP reinforcement method can reduce the amplitude of the stress intensity factor at the crack tip, inhibit crack propagation, and improve the fatigue life of the rib-to-deck detail. The cyclic cohesion model derived in this paper can adequately describe the damage evolution behavior of the adhesive layer interface under fatigue loading. The adhesive layer interface damage initiates at the weld toe of rib-to-deck detail, and gradually extends towards the longitudinal rib and both ends of the bridge deck.