In the context of examination-oriented education and the pressure of college entrance examinations (known as the "Gaokao"), Chinese high school students often experience academic burnout. Previous research has shown that effort-reward imbalance (ERI) is an important predictor of academic burnout among high school students, but the underlying psychological mechanisms are not yet clear. To address this research gap, we surveyed 415 Chinese high school students (226 males and 189 females, mean age = 15.82 years, SD = 0.87), and a self-report questionnaire including the ERI scale, school connectedness scale, academic buoyancy scale, and academic burnout scale was completed by all participants. The data were analyzed by SPSS 24.0 and the PROCESS macro and developed a moderated mediation model incorporating school connectedness and academic buoyancy. The results showed that (1) ERI was significantly and positively associated with academic burnout among high school students; (2) school connectedness partially mediated the relationship between ERI and academic burnout; (3) academic buoyancy moderated the link between ERI and school connectedness, as well as between ERI and academic burnout. These findings are not only valuable for understanding the underlying mechanisms linking ERI and academic burnout but also contribute to the development of intervention programs (e.g., interventions based on academic buoyancy) aiming at reducing high school students' academic burnout.