A sound maintenance policy of wind turbine occupies an important position in reducing the operations and maintenance (O&M) costs. However, few papers consider system performance, e.g. system availability, reliability, mean time to failure, into the maintenance policy. A novel optimal maintenance policy based on the performance-based contract (PBC) is presented to maximize the profit of suppliers meanwhile improving the system availability. Here, three maintenance actions are adopted: opportunistic maintenance, preventive maintenance and corrective maintenance. In precious researches where the objective was to minimize the O&M costs or maximize the system availability, while in this paper the maximum profit was used. To compare the proposed policy with conventional policies, three criterions are presented: maximum profit, greenhouse gas emissions and system availability. Finally, an illustrative numerical example is provided to demonstrate the applicability and superiority of the proposed model. (C) 2018 Elsevier Ltd. All rights reserved.