To　the　early　weak　damage　of　the　roller　bearing　and　other　rotating　machinery,　an　enhanced　resonance　demodulation　method　based　on　delayed　correlation　pretreatment　and　entropy　threshold　of　wavelet　packet　coefficients　is　proposed　to　solve　the　difficulty　in　determining　the　resonance　bands　in　the　traditional　resonance　demodulation　technique.　In　this　method,　the　weak　damage　signal　should　be　preprocessed　by　using　delayed　correlation　analysis　method　firstly.　Then　wavelet　packet　transform　is　carried　out　to　find　the　Shannon　entropy　of　all　leaf　nodes　coefficients,　an　effective　threshold　is　set　on　the　basis　of　the　entropy　spectrum　to　choose　the　leaf　nodes　coefficients,　reconstruct　the　signal,　then　do　spectrum　analysis,　and　extract　the　resonance　modulation　bands　effectively.　Then　use　the　envelope　demodulation　method,　and　successfully　extract　the　early　impact　characteristics　of　a　weak　damage　signal　of　the　machinery.　The　analysis　results　of　roller　bearing　experimental　data　confirm　the　feasibility　and　validity　of　this　method.　©　2010　Journal　of　Mechanical　Engineering.