Through　analyzing　the　shape　of　screw　of　oil　extraction　progressing　cavity　pump,　the　spiral　surface　equation　of　screw　was　established;　and　from　the　relative　motion　between　formed　milling　cutter　and　screw,　the　basic　profile　equation　of　formed　milling　cutter　was　established　with　the　method　of　non-instantaneous　envelope.　According　to　the　actual　use　of　formed　milling　cutter,　aim　at　the　problem　of　wear　for　formed　milling　cutter,　established　profile　equation　of　front　cutting　edge　and　constant　back　cutting　edge,　and　finally　to　get　a　complete　profile　equation　of　formed　milling　cutter.　The　correctness　of　milling　cutter　profile　is　ensured　by　interference　checking　for　profile　equation　of　formed　milling　cutter.　The　profile　equation　of　formed　milling　cutter　provides　a　theoretical　foundation　for　the　design　and　manufacture,　and　it　would　have　great　significance　to　the　actual　production.