Aiming at the problems of over-maintenance or under-maintenance in existing maintenance strategies for wind turbines, this paper proposes an availability-based combined maintenance strategy by comprehensively considering the economy and efficiency of wind turbine operation. First, an improved fourth-order Markov model is adopted to describe the state transition process of wind turbine components, and the availability of components is determined. Then, taking the minimum average maintenance cost rate of the wind turbine system as the objective function, a sparrow algorithm is used to solve the maintenance model, and the optimal maintenance strategy is finally determined. Finally, taking the operation data of wind turbines as an example, a simulation analysis of the combined maintenance strategy considering availability is carried out, and the results verify the effectiveness and rationality of the strategy.