Recognizing the importance to combine the manufacturing system and the management system for machining operation planning, a new methodology is proposed in this paper to evaluate the economic aspect of an operation plan. To assure the quality of a machined part satisfying the required specifications, the manufacturing system acts as an alternative generator to provide meaningful and practical plans. Through costing analysis, the variable, fixed, and total costs associated with the machining operation are quantitatively determined. The management system, which functions as an evaluative mechanism, selects the optimal plan based on the defined goal. This proposed methodology has been used as a framework in designing an expert system. The system establishes the sequence of machining operation planning and search the optimal plan which integrates the considerations from both production engineers and managers, and balances their needs for a quality and productive operation.