This paper discusses how personal factors,campus environment and social support influence undergraduates' exercise behavior in Changsha through sport commitment with the methods of questionnaire and interview based on sport commitment theory. Results showed: 1) Personal factors,campus environment and social support have significant effects on the level of exercise commitment and exercise behavior of undergraduates in Changsha; each dimension of exercise  commitment  had significant  influence  on  undergraduates' exercise  behavior  in Changsha. 2) ...