The research aimed to investigate the participating motive, social support and relationship to physical activity in Macau high school students. It aimed to study the significant differences of variables of participating motive and social support and the relationship to level of physical activity. The research adopted questionnaires survey as the method of investigation and conducted in 2012. The subjects were 749 students at junior secondary level in Macao. A revised version of questionnaires was adopted to investigate the participating motive in sport, social support and the level of physical activity in students. The analysis focused on the present situation of sport participating motive, social support and level of physical activity. The second perspective of analysis focused on its relationship between different variables and level of physical activity. The data were analyzed by t-test, one way ANOVA, Pearson correlation and other descriptive methods. The results indicated the following information: 1. The participating motives vary in genders, grades, social clubs, sense of achievement and social needs; 2. The social support also indicated the differences between genders, grades, social clubs and professional teams. The support ranked differently with school, family and peer as the priority; 3. Positive correlation was identified between sport participating motives, social support and level of physical activities.