Abstract: The maintenance of offshore wind turbines operated under the irregular, non-stationary conditions is affected by the waiting time. A model for optimizing preventive maintenance strategy of offshore wind turbine based on reliability and maintenance priority was developed. Firstly, according to the weather accessibility, the maintenance waiting time was obtained adopting the queuing theory. Subsequently the wind turbine was treated as a complex structure system and the reliability of components and wind turbine were presented based on the waiting time. The imperfect maintenance time was primarily determined by the system performance and secondly by the components performance. In order to determine the maintenance activity and sequence, the maintenance priority was introduced considering the maintenance cost and the reliability improvement degree of system, and was calculated by data envelopment analysis（DEA）. Then the maintenance scope was optimized aiming at minimizing maintenance unit time cost. Finally, a case of offshore wind turbine was illustrated the effectiveness of the strategy, and sensitivity factors such as weather accessibility and maintenance time are analyzed to the proposed model.