The　vector　control　of　interior　permanent　magnet　synchronous　motor　(IPMSM)　needs　detect　the　position　of　rotor.　In　this　paper,　the　position　sensor　of　IPMSM　is　rotating　transformer　and　we　designed　the　decoding　circuit　based　on　AU6802N1.　At　last,　we　measure　the　rotor　position　through　the　control　system　based　on　TMS320F28335　and　do　the　test　without　load　to　verify　the　accuracy　of　the　rotor　position　detection.