Interfenrence　detection　is　a　crucial　problem　in　the　process　of　the　stationary　internal　toroidal　gear　machining.　This　paper　proposes　a　new　method　to　detect　interference　regions　in　3-axis　stationary　internal　toroidal　gear　machining.　With　this　method,numerical　control　machining　geometric　model　is　built　to　detect　interference.　Interference　regions　can　be　identified　effectively　by　comparing　intersection　point　between　detecting　line　and　spiral　tooth　flank　with　that　between　detecting　line　and　tool　sweep.　It　was　found　that　this　method　not　only　can　be　used　to　detect　local　interference　regions　but　also　global　interference　regions　according　to　whether　dectecting　line　and　not　processing　area　of　curved　surface　have　intersection　point.