Digital transformation is drawing attention as a management strategy that fundamentally changes the strategy, organization, process, business model, culture, communication and system of the enterprise based on digital. Open APIs are the foundation of digital transformations and enable rapid adaptation through building and expanding digital ecosystems. API governance has become a prerequisite as the API has become the power of digital business. This paper describes the role and importance of API governance and addresses the issues of open API management. It also describes the core components and functionalities of the API management system for open API governance and introduces API management solutions from leading vendors.