The　existing　rotor　initial　position　detection　for　sensorless　permanent　magnet　synchronous　motor　(PMSM)　has　some　common　issues　such　as　the　multiple　signal　injection,　complicated　process　and　dependency　on　the　parameters.　To　deal　with　these　problems,　a　novel　method　based　on　the　current　envelope　was　proposed.　The　high　frequency　fluctuating　voltage　signal　was　injected　into　the　estimated　two-phase　coordinate　system　only　once,　which　rotated　at　low　frequency.　The　positive　direction　of　permanent　magnet　was　obtained　by　extracting　the　reference　value　of　the　coordinate　system,　which　corresponded　to　the　maximum　value　of　d-axis　current　positive　envelope.　Furthermore,　the　rotor　position　was　determined　after　the　position　compensation.　On　the　basis　of　previous　process,　the　reference　value　of　the　coordinate　system　was　extracted,　which　corresponded　to　the　minimum　value　of　q-axis　current　positive　envelope,　then　the　more　accurate　rotor　initial　position　was　obtained　after　a　rotor　position　correction.　In　addition,　the　effect　of　the　injected　voltage　signal　on　the　presented　method　was　analyzed.　With　a　maximum　error　of　4.1°　and　an　average　error　of　1.8°,　the　experimental　results　show　that　the　proposed　method　is　simple　and　feasible.　©　2018　Chin.　Soc.　for　Elec.　Eng.