There is a problem of waste of resources in the dedicated path 1+1 protection strategy in the traditional optical network. In this paper, a priority shared link protection strategy is proposed. After detecting the link failure, the flexible optical transponder switches to the shared protection link, and rearranges the service weight according to the priority of the service and the requested frequency, and provides differentiated spectrum slot allocation according to the service weight. In addition, this paper proposes an optimal routing and spectrum allocation method that considering the physical network topology, the set of service requirements, and the proportion of high-quality services as constraints, and considering the minimization of the utilization of spectrum slots as the goal. The theoretical analysis and simulation results show that compared with the traditional 1+1 protection method, the proposed protection strategy can save up to 38% of the spectrum resources while reducing the network congestion rate, and maximizing the sharing of backup spectrum resources.