To accurately predict the dynamic reliability of the automated manual transmission(AMT) gear system in mining trucks, a rigid-flexible coupling dynamic model was developed. This model considers the flexibility of key components and the effects of internal and external load excitations. Dynamic load analysis was conducted for the sixth-gear and seventh-gear transmission, which are subject to high service frequency and harsh operating conditions. Based on this analysis, the dynamic reliability of these gear systems was evaluated, taking into account the fluctuating loads, degradation in component strength, and the correlation between component failures. The study identified weak elements in the AMT transmission system and provided insights into the reliability of the system and its components over service time. These findings lay the foundation for improving the reliability and performance of AMT gear transmission systems for mining trucks.