This study aims to suggest the ways of mutually beneficial cooperation between large companies and small companies in the field of telecommunication services. To achieve this goal, it attempts to introduce mutually beneficial cooperation plans based on horizontal relationships rather than vertical relationships among large companies and small companies. Research contents will suggest the similarities and differences of individual telecommunication companies by analyzing mutually beneficial cooperation plans of large companies and small companies based on domestic three telecommunication companies. It examines the perceptions of people who are engaged in large companies and small companies in order to enhance the recognition on the mutual cooperation of large companies and small and medium companies. Based on research results, it attempts the activation methods of mutual cooperation of large and small companies.