To accurately predict the dynamic reliability of the AMT gear transmission system for mining trucks, a rigid-flexible coupling dynamic model of the AMT gear transmission system was constructed, taking into account the flexibility of key components and the influence of internal and external load excitation. Dynamic load analysis was conducted for the sixth-gear and seventh-gear transmission systems with high service frequency or harsh loads. On this basis, the dynamic reliability of the sixth-gear and seventh-gear transmission systems of the AMT transmission was studied, taking into account the dynamic changes in the transmission system’s load, the component strength’s degradation, and the correlation between the failures of each component. Through research, the weak elements of the AMT transmission system were identified, and the reliability of the transmission system and its components over service time was obtained, laying the foundation for the reliability design and performance improvement of the AMT gear transmission system for mining trucks.