Noise　is　the　biggest　obstacle　that　makes　the　incipient　fault　prognosis　results　uncorrected.　According　to　the　theories　of　correlation　analysis　and　threshold　de-noising　by　wavelets,　wavelet　transform　domain　filter　(WTDF)　is　constructed.　WTDF　is　an　iterative　process.　By　selecting　the　process　parameters　adaptively,　WTDF　can　de-noise　signal　efficiently.　More　important,　the　faint　component　in　the　signal　will　become　stronger.　WTDF　method　is　used　to　analyze　the　signals　collected　from　a　bearing　that　has　incipient　unbalance　and　misalignment　faults.　Results　show　that　WTDF　is　effective　for　bearing　incipient　fault　prognosis.