Using a sample of 685 college students, this paper tests the mediating effect of loneliness on the relationship between social support and subjective well-being on the basis of a questionnaire investigation. The results show that:⑴Social support, life satisfaction, positive affect, negative affect and loneliness of college students relate to each other significantly;⑵Social support of college students has a positive effect on their subjective well-being;⑶The mediating effect of loneliness on the relationship between social support and subjective well-being is the part effect and superiority.