Title: Application of fuzzy methodology for KPIs implementation in manufacturing execution system Abstract: Performance evaluation is an essential part that contributes to the development and success of an enterprise, because it helps decision-makers to concentrate more on the most critical operations and elements considering the 20/80 rule. The performance evaluation can be operated at different levels corresponding to the hierarchical structure of enterprises. This thesis establishes a five-dimensional model using fuzzy mathematics and analytic hierarchal process to carry out performance evaluation at the intermediate level of an enterprise, manufacturing execution system (MES). The five dimensions are significance, frequency, predictability, observability and time sensitivity; each of them characterizes the critical operations and elements, while the operations and elements are measured by key performance indicators (KPIs) both from ISO 22400 and newly-defined.