Manufacturing execution system (MES) is a computer application system that integrates all relevant real-time information along every step in a manufacturing process. MES is essential for manufacturers for gathering real-time production line information, supporting manufacturing decision making and increasing manufacturing efficiency. MES is a must for operation control and lot tracking in the shop floor of a plant with complicated manufacturing processes, such as semiconductor manufacturing fab or TFT-LCD manufacturing plant. This paper presents the formulization of performance measurement of implementing MES from several quantitative and qualitative aspects by analyzing the basic functions and objectives of MES and interviewing with some senior consultants and MES related working staff. In addition, multi-attribute decision making technique, analytic hierarchy process (AHP) is used to decide the priority of these performance measurement indices. The results of this research will be useful for a company when MES is an existing system or is a To Be system.