This　paper　presents　an　identification　method　for　the　spindle　rotation　error　from　the　flatness　error　in　the　workpiece　surface.　The　spindle　rotation　error　is　identified　by　the　wavelet　transform,　Weierstrass　function,　and　power　spectral　density　(PSD).　The　flatness　error　comprises　various　errors　of　the　machine　tool,　such　as　spindle　rotation　error,　guideway　error,　motor　error,　and　ball　screw　error,　therefore,　wavelet　transform　is　used　to　process　the　measured　result　of　the　workpiece　and　the　signal　is　decomposed　into　high-frequency　and　low-frequency　signal.　Weierstrass　function　is　used　to　fit　the　spindle　rotation　error.　According　to　the　PSD　analysis　of　the　processed　signal　in　the　frequency　domain,　the　spindle　rotation　error　is　identified　from　the　measured　flatness　error,　this　method　provides　a　basis　for　the　identification　of　machine　tool　errors.