In the era of Industry 4.0 and digital transformation (DT), the way the manufacturing industry provides value has shifted from selling products to directly creating value for customers. The synergy between business and information technology is the most important criterium for DT. This study proposed an object-oriented ontology-based enterprise architecture (OOOEA) framework, based on the unified modeling language (UML), to connect and integrate all databases and modules of the enterprise’s existing information system (or ERP). The enterprise domain knowledge must be depicted to achieve business-IT alignment. This research starts from the physical and philosophical views of object-oriented ontology (OOO), pays attention to the essence of all things observed or understood in business operations, and constructs the core ideas of the OOOEA framework. The contribution comes from three aspects. One is to provide guidance for the first step of DT, the other is to propose a concise and applicable methodology as the basis for communication between employees at all levels, and the third is to verify the feasibility and effectiveness of the framework proposed in this research through a practical case study.