Focusing on the academic engagement and its influence mechanism for left-behind children can enhance their autonomy and passion, which is crucial for their future growth. Nevertheless, the factors that impact the academic engagement of left-behind children and the intricate interaction between these factors and their underlying mechanisms remain unclear. This study seeks to investigate the interconnectedness and cyclical functions of left-behind children's beliefs about adversity, teacher-student relationship, and academic engagement, considering both intrapersonal and interpersonal resources and the dynamic growth of children. A total of 613 left-behind children (Mage = 9.52, SD = 0.78) completed the measurements of adversity about beliefs, teacher-student relationships and academic engagement, and the data were provided in three waves (T1, T2, and T3). The results indicated an interaction between left-behind children's beliefs about adversity, teacher-student relationships and academic engagement. Specifically, teacher-student relationships and beliefs about adversity positively predicted left-behind children's academic engagement, and academic engagement significantly predicted left-behind children's teacher-student relationships and beliefs about adversity. The findings support the developmental resources model and the developmental ecology theory, and also suggest that there may be a virtuous cycle between beliefs about adversity, teacher-student relationships and left-behind children's academic engagement, respectively. These findings extend existing research on left-behind children's learning and have theoretical and practical value for improving left-behind children's academic engagement.