Abstract: In this paper, the re-sampling of tidal tape data at 5-second intervals and the method of elimination of strong earthquake noise are discussed.The polynomial fit smooth sample (PFSS) method is given in this paper. The PFSSsynchronizes tape reading, smoothing and sampling. The memory of the computer has already had sampling results in the light of the given interval as soon as the tape reading finishes. Since format translation and preprocessing are performed for the relevant points, computer time is minimized. And since only sampling results are stored, less computer space is required. So the PFSSis usefull for processing of tidal tape data of small interval and long duration.In order to check the results of the PPSS, analysis of power spectra is used. The calculated example shows that the PFSShas a good filtering function.Nakai method is used to eliminate distortion caused by a strong earthquake and an iterated procedure is given. The calculated results are checked by analysis of power spectra, top. The results of spectral analysis of observed data which have been corrected for earthquake noise are similar to the results of theoretical tide analysis.