Purpose: This study was conducted to identify in depth the physical activity experience and the social support of the national-based exercise program participants conducted by the Korea National Health Insurance Corporation. Method: Participants were six elderly women and two elderly men who participated in the Health-100-year Exercise for more than 6 months, and in-depth interviews were conducted from February to March 2019. Among the phenomenological approaches, this study chose Giorgi s research method to summarize the contents of the research through three steps of transcription, theme coding, and categorization. Results: To grasp text contents as a hollistic perspective through an analysis frame of four stages, the semantic unit segmentation, the transformation into the academic language, and the analysis process of integrating the converted semantic units into the structure were carried out. In the contextual structure statement and general structure statement, we could find a total of 90 semantic units, 17 sub-components, and 5 components. Emotional aspects such as facilities for smooth physical activity, the exercise program for the elderly, the meaning of the leader and relationship, support of family, support of friends and colleagues, support from local governments and government agencies, social aspects, and economic aspects were found in the types of components. Conclusion: In our society, which is undergoing a super-aged society, the interest of the elderly in health intervention is increasing, and it is asking for alternative solutions to these problems. Therefore, it is suggested that the results of the phenomenological study on the physical activity experience and social support of participants in the Health-100-year Exercise Program, a government policy program, provide a clue for the future of health promotion of the elderly, and a formation of a positive social network.