In order to effectively obtain the loading condition of the bench test of the hybrid transmission system (HTS) and provide load input for fatigue damage analysis of components, the structural model of the HTS was constructed to obtain the wheel end torque corresponding to different working modes under 13 different driving cycles. By eliminating invalid data, counting cyclic load frequency by rain-flow counting method, and extrapolating rain-flow matrix, the strengthened load spectrum corresponding to different working modes was obtained. According to the eight-level classification method, the continuous amplitude distribution was equivalent to the constant load. The final loading time was 185.98 h, which provided a benchmark load spectrum for the subsequent fatigue damage study of HTS components.