This　paper　focuses　on　the　NC　machining　simulation　for　the　worm-wheel　hob-cutter　in　a　double　plane　enveloping　toroidal　worm　drive　system.　Based　on　the　coordinate　system　which　is　in　accordance　with　the　NC　machine　tool　in　the　hob-cutter　machining　process　and　the　coordinate　transformation,　the　paper　introduces　the　tooth　surface　equation　of　the　hob-cutter.　Then　the　principles　and　methods　for　three　dimensional　modeling　of　the　worm-wheel　bob-cutter　in　a　double　plane　enveloping　toroidal　drive　system　are　proposed.　This　helps　to　the　3D　modeling　of　the　tooth　profile　of　the　worm-wheel　hob-cutter　in　MATLAB　system.　The　study　is　then　extended　to　the　analysis　of　the　worm-wheel　machining　precision　influenced　by　the　hob-cutter　machining　process　and　method　via　computer　simulation.　The　construction　design　of　the　worm-wheel　hob-cutter　is　presented.　Finally,　the　solid　3D　modeling　and　NC　machining　simulation　of　the　worm-wheel　hob-cutter　are　implemented　providing　approaches　for　the　physical　prototype　machining　and　for　the　design　of　machining　cutters.