This study explored the impact of academic stress on sleep quality among Chinese adolescents, examined the mediation role of negative affect and the moderating effect of peer relationships. In total, 858 students in this study from grade 7 to grade 12 completed questionnaires of sleep quality, academic stress, negative affect, and peer relationships. Structural Equation Modeling (SEM) was used to test the hypothetical model. The results indicated that, academic stress negatively predicts the sleep quality, and the negative affect partially mediated the relationship of them. In addition, the effect of academic stress on negative affect was moderated by peer relationships. The results mean that adolescents with more academic stress may have worse sleep quality, negative affect may act as a potential link from academic stress to sleep quality. Moreover, the effect of academic stress on negative affect is moderated by peer relationships. It means that higher levels of peer relationships helped reduce negative affect caused by academic stress and allow them to sleep better.