According　to　the　multi-body　system　theory　and　geometric　topology　analysis　method,　combining　the　geometric　structure　and　working　principle　of　thread　NC　grinder,　made　the　kinematics　analysis　for　each　parts　of　NC　grinder.　And　the　mathematical　model　for　geometric　topology　structure　of　grinding　machine　system　was　established;　the　precision　machining　equations　of　NC　grinder　was　deduced.　Furthermore,　the　paper　used　the　coordinate　transformation　principle　of　homogeneous　to　deduce　the　precision　processing　equation　of　NC　grinder,　all　of　that　was　based　on　the　moving　relationship　of　the　machine　tool,　the　workpiece　and　the　grinding　wheel,　and　got　a　kind　of　method　that　it　can　use　multiple　line　grinding　wheel　to　grind　small　radius,　small　screw　pitch　and　multiple　thread.　This　method　laid　a　theoretical　foundation　for　NC　grinder　machine　processing　which　used　multi-line　grinding　wheel　to　grind　threads,　and　improve　the　grinding　efficiency　and　precision　of　multi-line　grinding　wheel;　in　addition,　this　method　has　obtained　good　effect　in　grinding　thread　production.