<p>The gear transmission system, serving as the core component for power transmission in mechanical equipment, simultaneously withstands complex external incentives. Its health condition directly impacts the operational safety of equipment. In practical operation, faults such as tooth surface pitting, tooth root cracks, and bearing raceway spalling in gear systems often exhibit coupled occurrence characteristics. However, existing research has predominantly focused on single component fault, and investigations into the mechanisms underlying simultaneous multiple-component faults remain insufficient. This study establishes a nonlinear dynamic model considering multiple-component faults effects for the compound faults of gear root cracks and bearing raceway spalling. The time-varying meshing stiffness is employed to characterize the influence of crack depth on gear pairs, while an additional displacement function quantifies the dynamic effects of bearing spalling dimensions. The model comprehensively integrates critical excitation factors including dynamic transmission error, and input/output torque, constructing a simulation framework that covers healthy states, single component fault, and faults in multiple components scenarios. Simulation results reveal that under faults in multiple components conditions, time-domain impulse responses exhibit overlapping phenomena. In the frequency spectrum, the fault characteristic frequency bands are distributed in the high-frequency range. Combined with envelope analysis, the fault characteristic frequencies can be effectively highlighted in the low-frequency range, clarifying the coupling relationship between faults. This study breaks through the limitations of single component faults diagnosis, providing new insights for mechanism analysis and feature extraction of simultaneous multiple-component faults under complex operating conditions.</p>