There　is　a　nonlinear　disturbance　problem　in　the　operation　of　large　inertia　load　space-driving　mechanism,　which　seriously　affects　the　normal　operation　of　the　system.　A　14　degree-of-freedom　nonlinear　time-varying　dynamic　model　was　established　for　a　two-stage　spur　gear　system.　The　dynamic　equations　were　solved　numerically　based　on　the　Runge-Kutta　method.　The　correctness　of　the　dynamic　model　was　verified　through　experiments.　In　the　author＇s　previous　research,　the　transmission　error　and　dynamic　response　of　gear　system　was　analyzed.　After　the　establishment　of　the　dynamic　model,　a　comparative　analysis　of　the　load　response　under　different　inertia　was　performed　to　illustrate　the　importance　of　studying　large　inertia　loads.　A　large　inertia　load　transmission　error　experimental　device　was　set　up　to　collect　and　process　the　transmission　error　data　under　different　load　inertia　and　different　speeds.　Comparing　experimental　results　with　numerical　results,　the　correctness　of　the　numerical　model　was　verified,　and　the　reasons　for　the　differences　between　the　two　were　explained.　The　analysis　of　the　experimental　results　shows　that　for　the　transmission　error　of　large　inertia　load　gear　transmission　system,　the　influence　of　stiffness　excitation　on　the　transmission　error　amplitude　is　dominant.　For　the　high-speed　gear　system,　the　pitch　error　plays　a　dominant　role.