Social avoidance is the behavior of an individual who actively avoids social situations, avoids peer groups, and seeks solitude during social interaction. Higher education students are particularly vulnerable to social avoidance. Social avoidance not only affects peer relationships and future development but also generates negative emotions, which seriously affect the psychological health of high school students. The ecosystem theory suggests that individual development is influenced and constrained by many environmental and social factors, and the causes of social avoidance in higher vocational students can be further explored from the micro-system level. Based on the “cognitive-behavioral” model, the network compensation theory of psychological needs, and the ecosystem theory, we not only examined the social environment factors, i.e., the causes of social avoidance due to cell phone dependence, but also explored the internal mechanisms affecting adolescents’ cell phone addiction from the aspects of self-control and peer support. Therefore, in order to examine the relationship between cell phone dependence and social avoidance among senior high school students, this study intends to construct a moderated mediation model to examine the relationship between cell phone dependence and social avoidance among senior high school students and to test the mediating role of self-control and the moderating role of peer support. Through a random sampling method, 600 senior vocational students in Heilongjiang were used as subjects and were surveyed with the Self-Assessment of Cell Phone Use Dependence Questionnaire, Self-Control Scale, Peer Support Questionnaire, Social Avoidance, and Distress Scale. The results showed that: (1) cell phone dependence positively predicted social avoidance among senior students; (2) self-control mediated between the two; the findings of this study have theoretical significance for reducing social avoidance among senior students.