The　fault　diagnosis　of　wind　turbines　under　nonstationary　conditions　is　still　challenging.　This　paper　proposes　a　novel　tacho-less　generalized　demodulation　(NTLGD)　method　for　the　wind　turbine　fault　diagnosis.　First,　one　instantaneous　frequency　is　extracted　from　the　time-frequency　representation　of　the　vibration　signal.　Second,　a　novel　phase　function　design　method　is　developed　based　on　the　extracted　frequency,　by　which,　different　from　traditional　methods,　the　fault-related　frequencies　are　mapped　into　the　fixed　predefined　values.　Then,　the　bandpass　filters　are　designed　according　to　the　designed　phase　functions　to　separate　the　mapped　frequencies.　Finally,　the　diagnosis　template　is　constructed,　and　the　fault　is　localized　by　matching　the　peaks　in　the　demodulated　spectrum　with　the　spectral　lines　in　the　template.　The　method　is　evaluated　by　the　vibration　signals　of　support　bearings　and　the　planetary　gearbox　in　a　test　rig　of　wind　turbine　drive　train.　The　results　demonstrate　that　the　proposed　method　can　well　pinpoint　the　fault-related　frequency　components　without　a　tachometer　and　the　demodulated　values　are　independent　of　speed　profiles.　©　2023