The　vibration　excitation　of　the　rolling　mill　mainly　comes　from　the　gearbox　in　the　process　of　rolling　strip,　and　the　meshing　excitation　is　the　main　excitation　factor　of　the　gearbox.　And　the　gear　backlash　plays　an　important　role　in　the　meshing　excitation.　However,　the　backlash　is　inevitable　in　the　process　of　designing　the　gear　system.　Therefore,　it　is　important　to　select　the　appropriate　gear　backlash　to　reduce　the　vibration　amplitude　of　the　gearbox,　to　improve　the　rolling　speed　and　the　quality　of　the　steel　strip.　So,　in　this　paper,　the　effect　of　the　different　variation　amplitudes　for　the　time-varying　gear　backlash　(TVGB)　on　the　vibration　characteristics　of　the　gear　system　under　various　mesh　parameters　is　studied.　A　new　formulation　for　calculating　nonlinear　damping　and　time　varying　meshing　stiffness　is　applied　in　this　coupling　model.　The　results　show　that　increasing　of　the　load　torque,　the　damping　ratio,　the　system　parameter　or　decreasing　the　directional　rotation　radius　variation　or　kinematic　transmission　error　caused　the　effects　of　variation　amplitudes　for　the　(TVGB)　on　the　dynamic　characteristics　of　the　gear　system　to　decrease.　Test　data　from　a　gearbox　experimental　table　verifies　the　accuracy　of　the　model.　The　model　is　shown　to　be　capable　of　simulating　the　mutually　coupled　effect　between　the　backlash　and　the　different　parameters　on　the　gear　system.　So,　the　new　coupled　model　can　be　used　as　guide　to　select　the　appropriate　gear　backlash　values　for　the　rolling　mill　under　different　operating　conditions.