In　order　to　further　improve　the　bearing　capacity　of　plastic　gears　in　the　transmission　of　metal　worm　and　plastic　helical　gears,　the　force　characteristics　of　the　traditional　equal-pitch　worm　helical　gear　meshing　transmission　were　studied　in　depth,　and　the　unequal　pitch　meshing　of　the　worm　and　the　helical　gear　was　innovatively　proposed.　Based　on　beam　bending　theory　and　gear　tooth　deformation　theory,　the　relationship　between　tooth　surface　load,　deformation　and　contact　stiffness　is　obtained.On　the　premise　that　the　bending　deformation　rate　of　the　gear　tooth　root　is　equal,　the　theoretical　design　method　of　unequal　meshing　is　deduced,　and　the　pitch　adjustment　of　the　worm　in　the　case　of　unequal　pitch　meshing　is　obtained,　which　is　verified　by　static　strength　experiments.The　experimental　results　show　that　the　unequal　pitch　design　can　increase　the　load-bearing　capacity　of　the　plastic　helical　gear　by　13.69%.　©　2022,　Editorial　Board　of　JBUAA.　All　right　reserved.