With the rapid development of offshore wind power industry, the operation and maintenance (O&M) requirements of wind turbine are continuously increasing. And the existing low-efficient of extensive O&M management restricts healthy development of the wind power industry. Hence, in order to improve the automatic management level of the offshore wind farms and optimise the coordination of resources, the O&M management technologies were implemented with the idea of lean maintenance, repair and overhaul/operations (MRO) in this paper. With the analysis of the O&M business characteristics and the management status of offshore wind farms, the main business functions and workflows of the MRO system were designed. And the maintenance bill of material (BOM), MRO planning and an improved AB2C inventory control strategy which was proposed and applied to spare parts inventory management were researched to optimise the O&M business processes. As a case, the MRO management software has been applied to the Shanghai Donghai Offshore Wind Farm, which effectively achieve lean management of the wind farm.