Objective: To explore the relationship between subjective well－being, self－identity and internet addiction disorder among undergraduates. Methods: A survey research method was used among 200 undergraduates which includes IUS, SWLS, PANAS and self－identity scale. Results: Positive emotion had significantly positive relationship with internet addiction disorder, but not with self－identity. The relationship between negative emotion and internet addiction disorder was not significant. Self－identity had significantly positive relationship with negative emotion and life satisfaction, and significantly negative relationship with internet addiction disorder. Internet addiction disorder could significantly predict self－identity. The relationship between internet addiction disorder and self－identity was moderated by negative emotion. Conclusion: There is a significant relationship between internet addiction disorder, self－identity and subjective well－being. Self－identity could predict internet addiction disonder, and negative emotion could moderate the relationship between them.