We　present　a　new　time-varying　mesh　stiffness　model　using　polynomial　function　with　regard　to　the　time-varying　mesh　stiffness　of　the　high-bevel　gear　of　a　radar　device.　By　analyzing　the　revolution　speed,　load　torque　and　damping　factor,　we　build　the　mesh　stiffness　model　and　the　nonlinear　dynamic　equations　of　the　high-bevel　gear.　We　compare　the　proposed　mesh　stiffness　model　with　traditional　rime-varying　mesh　stiffness　model　of　multi-order　harmonic　superposition　and　reference　data　model　of　time-varying　comprehensive　stiffness.　It　is　shown　that,　with　small　damping　and　overload,　the　proposed　model　is　much　closer　to　the　actual　characteristics　of　the　time-varying　stiffness.　This　model　lays　a　foundation　to　study　the　gear　transmission　dynamics,　such　as　vibration　damping,　noise　reduction,　smooth　transmission　and　other　aspects　with　small　damping　and　overload.