The　wire　electrical　discharge　machining　with　a　rotary　wire　electrode　is　a　new　technology　of　WEDM,　which　can　realize　high　machining　quality　as　WEDM-LS　and　low　price　and　operation　cost　as　WEDM-HS.　The　machining　mechanism　of　WEDM　with　a　rotary　wire　electrode　is　researched　in　this　paper.　The　main　reasons　of　improving　machining　quality　by　WEDM　with　a　rotary　wire　electrode　are　that　on　the　one　hand　an　inertia　force　effect　of　high　speed　rotation　makes　the　stiffness　of　the　wire　stronger　and　the　stability　of　the　wire　in　space　better　and　the　vibration　of　the　wire　less,　on　the　other　hand　the　wire　electrode　of　high-speed　rotation　has　the　effects　of　both　cutting　and　grinding.