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.