Outsourcing has become an effective production and management measure to increase the resource utilization and production efficiency. However, performing a sustainability evaluation of the outsourcing faces some difficulties in constructing a unified dimensional evaluation model for integration of the quality, time, logistics cost and resources consumption. This paper proposes an emergy-based sustainability evaluation method for the outsourcing machining resources for improving resource utilization efficiency. Firstly, the scope and boundary are defined, and the processes of the method and preparation are illustrated. Then, emergy models for the sustainability evaluation that comprise production quality emergy, production time emergy, production logistics cost emergy and production resources consumption emergy models are established. An integrated assessment is performed to acquire a best plan of outsourcing machining, and the corresponding evaluation indicators can be determined. Finally, a case illustrates the practicability of the proposed method laying a foundation for sustainability evaluation and selection of the outsourcing machining resources.