We apply four interpolation methods including linear interpolation,Hermit interpolation,cubic spline interpolation and trigonometric function interpolation to extend the high and low tide data of different tidal types in Chinese coast to hourly data,verify them by the hourly data of the tidal tables,and compare the errors of results of different interpolation methods from the perspectives of hourly data error analysis,harmonic parameter analysis and project tidal levels (including design water levels and tide riding water levels).The results show that for the error of hourly data，all the four methods results have a relative big error in the diurnal tide sea area of Beibu Gulf,but for other stations,the Hermit interpolation method is the best,followed by the trigonometric function interpolation method.For harmonic parameter and project tidal levels,the Hermit interpolation and trigonometric are better than other methods.