With the development of science and technology, buying has become much easier. At the same time, however, impulsive buying has many negative consequences for college students, and the causes of impulsive buying should therefore be explored. To explore the relationship between social exclusion and impulsive buying and its underlying mechanism, this study used the Social Exclusion Scale, Self-Esteem Scale, Risk Preference Scale, and Impulsive Buying Scale to investigate the roles of self-esteem and risk preference in the relationship between social exclusion and impulsive buying among 768 college students (387 were female, Mage = 20.25 years). The results were as follows: (1) when controlling for gender, age, family monthly income, and monthly living expenses, social exclusion significantly and positively predicted impulsive buying; (2) self-esteem played a mediating role between social exclusion and impulsive buying; (3) risk preference moderated the relationship between the second half of the mediating path and the direct path. These results reveal the mechanism underlying impulsive buying in college students, that is, social exclusion will predict the decrease of college students' self-esteem, and low self-esteem will further predict college students' impulsive buying which is a way for them to gain a sense of self-worth. Relatively low risk preference can well alleviate the negative impact of social exclusion and low self-esteem on impulsive buying. What’s more, these results have implications for impulsive buying interventions. Schools should aim to create a good peer atmosphere by making certain rules that help to reduce social exclusion and parents and education departments should cultivate students’ risk awareness to avoid risk behaviors in college students, such as impulsive buying behavior.