The business environmental structure is constantly being shaped by customer's desires and market dynamics. A large number of loosely interconnected participants make up a business ecosystem, and offers a customized and complete set of products and services. In a business ecosystem, the competitiveness of a company is influenced by its own capability and its interrelated partners' capabilities. Therefore, a company should enhance not only its competitiveness but also related companies' capabilities. To do this, a company has to find its place in the business ecosystem to make a complete business strategy using IT. This paper provides business ecosystem strategies and academic guidelines from the perspective of a single company. Firstly, a business ecosystem perspective is conceptualized, and the importance of a keystone company's role in the ecosystem is examined. Then, using a case study method, focus is put on the keystone's IT capabilities that pave the way for a healthy business ecosystem. This paper explores the Korean Capital Market as an example of a business ecosystem and finds the role of IT, particularly from the perspective of a keystone company. Through this study, it is confirmed that the keystone company's IT capabilities play an important role in the healthy business ecosystem. This paper provides guidelines to practitioners in keystone companies and gives ideas to IT researchers.