The importance of access control and communication security in wind farms is discussed according to the security needs of international standard IEC 61400-25 and in depth analyses of the security of monitoring and control communication process. In accordance with IEC 62351， an access control module based on role based access control（RBAC） to achieve authorization and access control， and secure communication module utilizing TLS coding packets—MatrixSSL are built respectively to realize integrity， confidentiality， and authentication of data exchange. Finally a model of agent mechanism based on the access control module and secure communication module is constructed. An application to the wind turbine controller is modeled and analyzed to demonstrate the realization of the security agent mechanism. Based on the information model and information exchange model proposed in Standard IEC 61400-25 and considering embedded environment of wind turbine units， this design complies with international safety standard IEC 62351， and meets the demand of monitoring and control communication security in a wind farm.