This　paper　first　develops　a　mathematical　model　for　the　dynamic　characteristics　analysis　of　a　toroidal　drive.　This　model　allows　the　analysis　of　a　toroidal　transmission　with　any　numbers　of　planet　worm　gears　distributed　around　the　sun　worm　and　any　numbers　of　spherical　rollers　distributed　around　the　planet-worm　gear.　In　the　modeling　process,　distinguished　with　other　kind　of　gear　transmission　modeling,　the　planet-worm　gear　tooth　(spherical　roller)　is　considered　as　independent　components　in　the　toroidal　drive　system,　the　vibration　modes　are　classified　into　planet-worm　gear,　spherical　roller　and　translational　modes.　Further,　the　characteristics　of　the　vibration　amplitude　and　the　Eigen-value　number　of　different　modes　are　analytically　investigated.　©　2010　IEEE.