A　speech　enhancement　approach　using　adaptive　wavelet　threshold　and　spectral　subtraction　in　the　wavelet　domain　is　proposed　in　this　paper.　First,　in　order　to　maintain　the　linear　phase　and　prevent　the　spectral　aliasing　of　reconstructed　signals,　the　noisy　signals　are　decomposed　by　un-decimated　bi-orthogonal　wavelet　packet.　Second,　spectral　subtraction　is　used　for　reducing　noise　from　the　two　low-frequency　sub-bands,　which　avoids　the　excessive　distortion　of　low-frequency　components　caused　by　wavelet　de-noising.　Next,　the　improved　wavelet　shrinkage　algorithm　is　adopted　in　the　other　high-frequency　sub-bands.　This　threshold　is　updated　by　adaptively　tracking　the　level　of　noise.　Finally,　these　modified　wavelet　coefficients　are　reconstructed　to　obtain　the　enhanced　speech　signals　by　the　inverse　wavelet　packet　transform.　The　experimental　results　show　that　the　proposed　approach　outperforms　spectral　subtraction　method　and　wavelet　de-noising　method.